What sort of cars should I be looking for, for a 3.90 or 4.11 diff? It would really be righteous if I could get a LSD with it.

Subaru STI R180 2005 2006 see http://forums.hybridz.org/index.php/topic/78123-subaru-wrx-sti-r180-side-axles/

Mine isn't LSD, but it's a lot of fun. R180 4.11 out of the front of a Nissan 4X4.

I'm also running an open R180 with 4.11s out of an 84 4X4. I love the ratio but it probably wouldn't be the best choice for a commuter car. It was a bolt-in install on my 72 but that may not be the case on a 77.

I should've added that a 4.11 would be bad with the original 4 speed. I'm running an '82 ZX 5-speed. I'm actually turning ~500 RPM less now at 70mph than the original combo...

I am running a late 70s 5-speed I believe. Mine turns 3500rpms at 70ish on 205/60/r14s in 5th.

Rpms depends on tire size, diff ratio, and trans ratios. If freeway rpms are a concern, this will help figure it out before you commit to anything: http://webspace.webring.com/people/cz/z_design_studio/

FWIW, I like the close ratio ZX transmissions with a low diff ratio. The ZX's came with a 3.90, so a 4.11 is not bad at all. Bad Dog's idea of lower rpms with the 4.11 and 5 speed is proved by the calculator.

Took the car our last night after I adjusted the valves and ran some sea foam through the intake. Holy crap 3rd gear in this car is LOOOONNNNNNNNNGGGGGGGGGG!