The Stovebolt Site Forums The Parking Lot '60-'66 Trucks Best Upgrades To Make The 235 Breathe Easier

There are other places you can get the headers, but I don't know anything about the quality of the parts or the service the vendors provide.

Fenton headers - Speedway Motors
Offy dual carb intake - might fit - Speedway Motors
Fenton headers - Classic Industries
Williams headers - Langdon's Stovebolt Engine Co
2 or 4bbl carb intake - Clifford Performance
Clifford headers - they claim a 18%-22% power increase

Better carbs and headers will help the 235 breathe better and produce more power. (People will argue about how much more power.) So will a mild cam. If you want to spend a lot of money (about $1600), you can bore the engine and get more power that way as well. Good mufflers that allow the system to breathe will help as well.

I did all of the above, but I've never put my truck on a dyno to see what it produces. (I'm going to have to check on that.)