Originally Posted by 78buckshot
It depends on several things, how many miles on the 366, how you want to use the truck if you swap motors, are either of the engines burning oil/smoking? The dieseling can be addressed and probably has nothing to do with the valve train. The 366 is a true truck engine, low RPM torque and heavy duty castings, the 454 is a good motor but not the same animal. The 366 probably has a Holley carb on it with an anti-diesel solenoid and a governor, I can't say if the 454 has a governor but probably a Q-jet carb, both carbs can be rebuilt if they have not been tuned with a hammer. Just a gut feeling here-I would keep the 366 in it.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy