On a 351C/M the thermostat housing will be on the block where as a 302 or 351W has it on the intake. The fuel pump mounting on the 351M will have a vertical bolt pattern a 302 / 351W will have a horizontal pattern. The 351C uses a standard small block bellhousing bolt pattern but the 351M/400M has the larger 429/460 bolt pattern If you determine it is not a 351 C/M then look at the front of the block and compare the distributor and intake mounting surface, on the 302 the will be almost even in height on the 351W it will be over an inch difference
it usually is, a torrent of adult malt beverages befell us yesterday, and the sun was hidden. It also was last weekend for the All Ford show @ Silver Springs. 961 cars, and about 20 to 18 Mav-Comets.