As described in my posts going back to day One for this group, I'm running an Edelbrock 1400 bolted to an Edelbrock Performer intake, 3" exhaust all the way through a Freeflow muffler. I also have stainless headers. The engine is a crate built by Delco Remy, the transmission was reman and sold with a new torque converter. The brakes are also new and don't drag. There are about 2,000 miles on everything in the drivetrain since I installed it about 5 years ago. It does "want" to go fast, but I keep a light foot on the throttle. I have so much dough in the whole shebang that I'm reticent about even more on an over/underdrive.
One thing that makes tuning difficult is that the new flywheel wasn't marked to match the timing marks on the pulley, so accurate timing is entirely by ear.

I do have the original distributor and electronics, which might be the culprit. Maybe. I would love to have EFI, if only for reduced emissions, cold starting and high altitude driving.