Zed Head

I think that you have the math down about perfectly. EuroDat supplied the final clue to your problem early on. There is no "70-74" pressure plate (tall plate) available in the common low budget aftermarket. There are only two kinds now, a 225 mm plate (coupe) and 240 mm plate (turbo and 2+2). If this forum had stickies this would be a good one. That's a nice illustration of where to measure.

Looks like you've got the math figured out. You could probably measure more on your old collar and bearing and use the illustrations from MSA and ZCarDepot and figure out if their product would work. Have to do some scaling and rithmetic and ratios and thinking... It's probably this one. More bad illustrations. Good luck. Hopefully somebody out here has one. @zKars https://www.thezstore.com/page/TZS/PROD/21-2122

This picture is confusing because the measurements shown are only valuable for comparing between them, and because the type of transmission, either type A or B or number of gears, is irrelevant. It's just a bad illustration. The measure that has value is not shown, from the surface of the bearing to the surface of the ears. Even the aftermarket guys are confused about the sleeves/collars, every one of them shows a worthless dimension. I would forget about "A" collars and "B" collars. Figure out a way to get the distance from the surface of your pressure plates springs (where the TO bearing contacts them) to the flywheel (which you almost did, but never finished) and post that up. Someone out here probably has the collar you need, and knows how to get the measurement that will add up to 92 mm, and will send it for a few dollars.

Is the car level? If the back end is high you might have overfilled, the fluid is sitting in the front of the case. Or if it's tilted sideways, the fill hole might be high. I've always used less than the capacity shown because of fluid that didn't drain out. I always lift both front and back end also to keep things level.

You should ask about the front mount also. Why not? The tools are probably all in the same spot. http://www.carpartsmanual.com/datsun/Z-1969-1978/axle/rear-suspension/16

zcardepot might be interested. @zcardepot.com

Here's a shorter thought - Nissan got rid of the mustache bar design when they went to the ZX body. And they modified the parts a few times over the years. It's really just a bad design from the beginning. Simple ideas should be possible for easy improvement.

No offense intended to anyone that has posted on this topic. But some of these things just need to be experienced to be understood, I think/guess. Carving up a piece of solid metal leaves an obviously strong part behind, made of metal. But, if you go out and buy a piece of Steel Stick, or one of the other metal-filled epoxies, and try it out you'll understand how strong it can be, if prepared properly. "Epoxy" is a nebulous word, the variety is large. The same goes for polyurethane. Rubber is used in the automotive industry because it's cheap. If you've ever worked for a company that supplies automotive parts you'll understand how every fraction of a penny matters to the automakers. They'll spend hundreds of thousands on engineering staff to design a part made from the cheapest materials. Because the volume of parts is so high. Making rubber parts cost quite a bit in tooling also. Rubber parts are not poured, they are formed via pressure from rubber sheet or other solid form, and cured using heat. I don't think that anyone is going to reproduce the rubber parts, in rubber. I'm just posting options. But nobody can really discount them off-hand without taking a closer look. When I was messing with my mustache bar I bought some big rubber washers from the local hardware store and stacked them up to take up the space that the worn out scalloped washer used to fill. AK260 could try that instead of carving up a PU bushing. There are endless ways to get the big old chunk of mustache bar steel to stop moving around, clunking, but still avoid transmitting sound.

Here's a biased article from a company that makes PU products. http://harknessindustries.com/rubber-polyurethane/#:~:text=Polyurethane has higher abrasion%2C cut,has better load bearing capacity.&text=Finally%2C polyurethane looks better than,better than its rubber counterpart.

I think that the commercially available replacements bushings were all made from a hard (high durometer) PU just because it was easy and cheap. Probably chosen for a single application like the smaller front control arm bushings then they just started looking around for any rubber part that could be replaced, using the same material. You can get PU in super-soft to brick hard. An 80A would be pretty soft but firm. PU's are very versatile, you can't discount all PU's because somebody in the past used them for the wrong purpose. You just have to pick the right one. https://www.polyglobal.co.uk/a-guide-to-shore-hardness/#:~:text=Polyurethanes are most commonly used,maintain their profile under pressure.

Here's a start along the lines of what CO has been suggesting, the google search below. It might be distasteful to many, because it seems "hacky," but a person could fill the void of an undersized bushing with metal-filled "space-age" epoxy (AKA JB Weld) and probably have a nice solid bushing assembly. https://www.google.com/search?q=motor+mounts (browse the images) https://www.jbweld.com/product/steelstik-epoxy-putty-stick https://www.jbweld.com/products

I can't remember who it is (anybody?) that is reproducing the small rubber parts but he would probably have the experience to make an attempt at it. Here's another good link. Understanding how to create a good mold, following instructions, and knowing what can screw things up (moisture, contaminants, etc.) are the key. https://www.fibreglast.com/product/introduction-to-urethane-casting-resins/Learning_Center

Is that the same car? Bumpers, wheels, side trim, and dent look different. Still, both look good. Thanks for answering the 5 speed question.

You could pour your own. https://itwperformancepolymers.com/products/devcon (type urethane in to the search box) https://www.flexsealproducts.com/

I bet if you looked at things like the brakes shoes and pads and rotors and wheel bearings and general grease buildup on the diff and axles you could feel better about a guess. The talk about rust and mileage is kind of overlooking the replacement cost of those interior parts. You could probably put a list together and price each part individually and $8,000 would seem like a good deal. I kept a list of my costs just to get an old 76 in decent shape and I was over $5,000 pretty quick. $50, $200 there....it adds up.