https://www.ford-trucks.com/forums/8...ne-i-have.html
thats the link to my other thread can anyone help me figure out which engine i have?

 

Youve been told already, its a 351m/400, this two engines share everything excpet for the pistons and crankshaft, so they are virtually identical. The 351m was introduced in 1975 and the 400 in 1971, so if the truck is still original and you hace a pre 74 truck you have a 400, otherwise check your vin code, I dont remember exactly were the letter should be but its in the firts 4 digits, so an "S" in the first 4 digits means a 400 and a "H" means a 351m..... If its still unclear measure the stroke ( 3.5" = 351m - 4" = 400), you can also check the crank for a cating code (351m = 1k - 400 = 5mab)..

This is all the info you can possible get to identify your engine, good luck