On the spec sheets, it says the recommended head gasket is a Fel Pro #7733PT-2. On Summit it says that gasket has a 4.125" bore. Would that be ok for a 383 which is (I believe) 4.030"? Also, what's the biggest you could go on the bore on the gasket? Would 4.166" be ok?

Thanks!
-Josh

Ideally, the bore diameter of the head gasket really shouldn't be any larger than the cylinder bore size...at least in theory. The larger the head gasket bore is, the more compression you stand to lose. Granted, it ain't much, but you also have a better chance of the gasket failing prematurely.
Then again, on some engines, the valves actually intrude into the cylinder bore, requiring a bit of a notch to be ground into the top of the cylinder to clear the valve.
In the case of a specialty engine, such as a stroker, I'd go with what the builder recommends.

Josh, Yes you can use that gasket. The largest bore gasket that you could use would be a 4.200. What kind of heads are you using? Are they aluminum? This is my opinion, maybe Joel might want to give his. And also Larry from Corvette Specialties. 

I didnt realize that Joel was already responding..........

Trick Flow definitely recommends the Fel-Pro 7733-PT2. For up to 4.060" bore they recommend Fel-Pro 1003. For up to 4.155" bore they recommend Fel-Pro 1010. I would definitely stay with their recommendations for their aluminum #23 heads.