interesting choice, but each to their own.
Personally if i was going to use a Capri as a daily i would just try to source the best shell i can, regardless of whether it is a 2.8 or not.
You can always make up strengthening brackets and buy some of the plates if required, but on a raod car it is not really needed.
I am building mine as a race car and have a 1.6 base shell as it was the best i could find at the time. I have made up gussets for mine and have fitted the inner wing walking plates found on the v6 cars (gussets can be bought £35 and the walking plates £60)
As for the transmission tunnel, sorry i don't know, but it is big to start with on Capri's, i am fitting eventually a 302 with T5, it will need some shaping with a hammer and a slight cut here and there, but it will be ok i reckon. But as for an auto box no idea. Easy to modify anyway.
Hope that part helps
Plans have changed to just make a good fun Track Car