Well, I am buying a 1975 Ford F100 Explorer from my uncle for $250. The motor that is in it is NOT stock. The cylinder heads on the engine are 352 heads, but he's not sure what the block of the engine is. Where do I find some sort of engine identification for the C.I.D.? He said that the 352, 360, 390, and 428 heads are all interchangable. Do y'all think the engine is a 352, or could it be something else. Would it make sense to put 352 heads on a 360 or 390? He also said that the engine makes a good 240 HP. Would a 352 make that much? What about a 360, or a 390?