Its not a 400M or 351M. Looks like a 352, especially if you said it has a tag that said 352. I am no expert on telling the difference between 352 and 390, I think the bell housing is the only difference by looking? The 390 and 360 has a rounded bell housing, the 352/428 have a bell housing simmilar to the regular ford big blocks like the 351M/400M/429/460.