I have a DIY ported stock TPI base off a corvette that I am getting ready to install on my motor and wanted to ask you guys what gasket would be the best choice.

It looks like almost everyone recommends the felpro 1205 gasket, however I was also looking at the felpro 1256 and though the port sizes are about half a hair smaller (1.99x1.23) than the 1205 these measurements still coincide with the ports on my manifold which I measured with a digital caliper. I want a gasket that is "just right" and don't want to get the 1205 only to realize it is too big.

Also, are you guys fond of the composite gaskets or the steel core laminate? Composite gaskets look nice however I have heard of the rubber seals separating from the gaskets and creating all sorts of problems. I have seen this first hand when a set of the composite gaskets failed in this exact manner on my dad's 4.3 in under a year but then again the mechanic that installed them kind of botched the job so I'm not saying with 100% certainty that it was the gaskets.

 

I can't answer your port size question. I would add that you should avoid the Fel-Pro Perma-Torque line and stick with their Print-O-Seal line.

Back in the day, I read someplace that the Perma-Torque gaskets didn't seal very well when sandwiched between cast iron and aluminum. Come to think of it, I think this was on the instruction sheet that came with my old Edelbrock 3860.

 

"stick with their Print-O-Seal line."

I have had good luck with the Felpro Print-O-Seal line myself.