I know, I know. It has been covered somewhat.

I have a TII rx7 with under 70k miles (s5) and a full Tii swap tranny etc (S4)
I know about the knock sensor and compression difference, other than that what's different?

I want to keep the original block in clean OE shape and use the swap one instead to play with, port job. What do you think?

 

So you want to put the S4 TII motor in your S5 TII? I believe any question you may have for this has been covered and there are a few build threads you can go through that might have even more answers.

Try searching just a little more or ask more detailed questions.