Welcome Rob, looks like you've already gotten into the swing and have been helpful. Fargin? Ya gotta love the www!

To perform, these engines gotta breath. Running out of oomph at 4k with a 3.08 sounds like you've got a rag caught in it (figuratively of course). Probably you need to figure out the heads, and carb, at least, before really pinning it down. You could be right about the cam being off a bit, or it could simply be timing, or the advance isn't functioning correctly. Carb should be 600-650 cfm if it's a mild cam, and "small" heads. I've gone to 750 but the engine really needs to move air to do that.

Your desire to keep the iron manifolds may fit the compartment restrictions, but they could impede your ability to improve the breathing. You didn't say whether they were the logs, or the ram horns. Ram horns flow slightly better, and the fuelie Vette versions have a larger outlet. Otherwise you may have to consider block hugger types, especially the "flat" collector Hookers.

You didn't state which model Camaro intake it was, but the factory manifolds were pretty good in their day. The older style Performer was essentially the same manifold (P/N 2101 I think?) but the newer ones are a slight improvement. Their newer airgap model might be better if you don't need any heat to the plenum for all around operation.

As for the trans, the 350, especially with the 3.08, should fit just fine. They'll handle all the torque a 327 will dish, and I agree with the Transgo over. say a B&M, for shift improvement. The extra gear in the 700 would be good if you were planning to drop the gear ratio into the 4's. It was the early models of the 700 that gave them a bad name, as well as the 200's that came about in the same era. The later 700's were corrected by GM on the fly, and have stood up well. Raising the stall is popular (though sometimes a boy racer thing), but really only has advantages if the car is pretty light, or you really need to get the launch into the power band.