I don't own that one anymore. Too bad, it was my favorite!
Go to my Capri page at http://www.geocities.com/adria-amber/capri.html
for a look at my current Capri.
Yes you can get parts. Performance stuff is rare but can be found. Yes the M II came with the same engine but so did the Pinto and the Ranger and Explorer. The 4.0 is an updated and bored and stroked version of the same block. I know someone who has a 4.0 in a '74 Capri with a T-5 behind it. I'm putting a T-5 behind mine too.