Go with 7.5 Mahles, you won't regret it.

HotRod, you could of course go with 8:1 if you want better off boost response and run less boost until you went EFI.

The stock 930 intake port in the head is about 36mm but it necks down to about 32mm at the intake.

Yeah, mine necks down to 33mm right at the intake, I haven't measured the plastic spacers yet to see what they are...or the heads

I'm magnesium welding my stock intake and then open the ports. Well actually Kevin at UltimateMW will do the porting.

Why the welding, wouldn't extrudehone clean them up and then just machine the intakes to whatever you want them to be?

I'm opening the ports to 41mm and so I need the extra alloy around the ports.
Stock intake does not have enough material around the ports to adequately seal after the porting is done.

My intake manifold was ported, along with the heads, don'tknow to what size though. This is a pic of a ported 930 manifold, not mine. Don't know if you can tell how much has it's been opened up from this shot?

http://i139.photobucket.com/albums/q...takeported.jpg

My ports look about that size and they are ported to 36mm. I'm doing an EFI conversion with bigger valves and 41mm ports on the heads. I'm also using 76.6 mm stroke crank and 98 mm mahles P/Cs for ~ 3.5L. It took weeks to nail down the magnesium welding technique.