I have a 37 pu and a 51 pu, both are powered by 261's. The 51 engine is more or less stock, the 37 has a M4F cam,small 4bbl, Fenton headers, and more compression,both have the same rear end gears.The 37 is probably 400 lbs lighter, but what a difference in performance.The 51 runs great, good pulling power, but the 37 pulls the same at low speeds and far better at mid and high speeds , the engine is far more free reving.It might be better to choose the right components from the beginning, but the stock 261 cam should be fine.Check your 261 cam casting number to be sure it is a 261 cam.
