On a mild motor, headers won't get you much till you get the RPMs way up there. Even then it is not a lot. If you are not inclined to fuss with headers, stick with the 2.5 manifolds, they work pretty good.
The difference between the 2 inch and 2.5 inch is more than it sounds like.
I seem to recall reading that with those Doorman manifolds you get two of the same (as pictured). So you either let the bracket stick back towards the firewall on the passenger side or grind it off. I think there is a cheap version of the 2.5 inch rams horn with out the bracket. I used expensive repros with correct casting numbers and such.
Thanks, it was actually your post that got me thinking about the ram horns. Do you know what the casting # is for a passenger side with AC? I keep seeing the 902 casting number as the ac one on forums, but every were I find it it comes back to a non AC vette motor.