Okay... I'm gonna take a stab at this and u tell me if this is what you're asking...

First of all since you're talking about switching heads and stuff I'm assuming we're talking B-Series heads... if not, this post wil not help ;-)

If you're going VTEC and u are turbocharging it you'll probably use either the B16A head or the B18C5 (ITR) Head because the combustion chamber is bigger... Slightly... leaving u with lower compression than the b18c1.

And therefore if u are going N/A and u have like... 10.2:1 compression pistons or something like that u can have the B18C1 heda and have a slightly higher compression and as long as u like to use 93 octane go for it.

As far as the size of the ports and all... They're similar to each-other and if you're porting and polishing **** it it won't matter anyways. lol Just tell them u want the ports "BIG." Say... "I WANT BIG PORTS." They'll do it. hehe

I hope that helped u out a little.

Harry