3/8″ pipe plug vs. 3/8″ Special thread on the “335” family oil galley.
351C Thermostat location on the block. Missing the brass restrictor.
351M/400 thermostat location on a block.
351M & 400 crankshaft. By looking at the hole in the crank pin and comparing it to the location it is in relation to the main and the radius seam, you can see the difference in a 351M & 400. 400 casting numbers: 5M, 5MA, 5MAB, 5MABC
Ford distributor differences: The 351W and the “335”, “385” series distributors are basically identical except the gear. Some say that the 335, 385 series is a long body. The 302 and 351W share the same gear OD. The aftermarket offers gears in 3 different IDs: .437″, .500″, .530″