Well all i would say is use a 1.0L carb if you want to but if you can get a 1.2 carb then it's best to use that. I've driven the egr setup and it was very smooth. I've driven the non egr 1.2 and that was very smooth too. And for 2 hours every day i drive a 1.2 with a 1.0 carb, not quite so smooth anymore when compared to the 1.2 with the correct carb on it. I found all 3 to have equal power in every respect, just a different exhaust tone.
But all that said; this is my experience and my oppinions, which may or may not be what you or others encounter. So really it's just down to what you want to do and what your budget will allow you to do. Remember to change the rear engine mount to a 1.2 mount, they're different as the MA12 has additional supporting brackets to hold it in place. You may also want to change the fan-belt pulley for the MA10 one so that you don't have to change your altinator for the tracked belt type (assuming that your donor engine has come from an egr/ecc set-up car).
