Instead of filling up the forum with a million separate questions, I decided to start a thread (which I also find to be more interesting to the people who know more than I do and, in turn, tend to be more responsive).

Here it goes, I have an A12 engine and transmission in my 1964 MG Midget that I am currently restoring (here is the thread on the restoration 1964 MG Restoration). I know next to nothing about Datsuns which is why I have come here.

I ran a compression test (mildly warm) which returned: 125, 115, 115, 112. Probably need rings.
What other areas should I be checking for wear? (end play and such?)
I'm going to install a complete clutch kit: PP, disk, through out bearing. How hard is it to install a new main transmission seal and rear engine seal?
As if jumping into a completely unfamiliar engine wasn't enough, I plan on having the manifold modified to accept two British SU carburetors. Wish me luck...