Another crossflow engine tuning question?

[Holbeam]

I have a 681f 6015 DA (tall block 1600) crossflow that is in pretty much standard condition eg chambered head, dished pistons....I also have a 711m "flat" head and (you've guessed it) I was wondering if the head could be swapped without much trouble and what the likely compression ratio increase would be. Cheers Mick.