Typical 72 400 should be pushing 220-250 HP. Then deduct HP for worn cam, rings and valve seats.

When you are pushing a 3.90 rear with a sub par 200 HP motor, you will definately feel dissatisfied.

The motor will depend on current cam, carb and calibration, heads, exhaust and intake.

I am a firm believer in doing something right the first time, after many errors and plenty of trial. If you are going to rebuild a motor, find someone who has sucessfully built Pontiacs. They are different than Chevies, Fords and Mopars. I once seen a guy install domed pistons to increase the compression in a 400 at a cost of $850 when the builder should have done was to buy and rebuild a set of heads. Same result in the end, but Pontiac heads were designed for flat top for optimal performance.

I would earmark at least $3500 for a complete rebuild including torque plate bore/hone, align check on mains, new ARP bolts for rods, SERDI cut on valves and the best hard parts (Ferreas, cam, pushrods) that you can afford. Included is having the rotating assembly balanced. Within that $3500, distributor recurve retrofit, carb rebuild..new everything.

Dyno session is a great investment if you can afford it. About $400 for 1/2 day $600 for full. The dyno shop will tweak the jetting and timing for optimal performance.

I have learned that building it right initially saves money overall.