I am running the 280 to its legal limit. I have an r200 diff, I have a 5 spd. The radiator opening is different is what I was told and what I was mentioning. Either way I will need a new radiator as mine was crushed. Rear drum is the same but there are a slew of internal parts which are listed as being different between early 240 and 280. I think that tha 73 brakes may have been the same internally. I may have the round ports. I forget which head I have but I think it is a pater p series head (zx?) Fuel pump and fuel tank were merely observations. The tub has been butchered to install a fuel cell. So I will have to go ahead with that. I think that if you pour money into an L24 it will make more power than the RX7 but will either car be a legal IT car when you are done? Lets here more suggestions. I don't want to get stuck midproject with suprises! Thanks Bryan