Not too big at all.
You could always get 205s and if you need more run the 225 program on them. I guess if I had the cake and your goals I'd go straight to 225s. I'd rather have a "too big" head and a smaller cam then have smaller heads and some monster stick that would be a PIA. If you're going to a block with a 4.125 bore and a turbo, why stay at 331, why not a 347 or 364? You must know more about turbo cars then I so you know the advantages of turbos and piston speed....
Adam