engine ID

i've got a 66 ford thats had an engine swap done sometime before i bought it, the old boy that had it had gotten sick and i purchased it from his daughter that didnt know to much about it. im pretty sure t originaly had a 352 or a 390 but like i said, someones done a swap. the motor thats in it i'm pretty sure is a late 60 early 70 smallblock, if anyone knows if theres some small thing that can tell me what the motor is or where the vin number is it would be greatly appriciated!

there will be a casting number on the heads under the valve cover, ussually states engine size... if its an FE series thats very unreliable..... also up in the spot the starter goes theres a number casted on the block.... also with your original vin# you can find out what motor the car originally would have had.... what model is this 66 ford?

it's a 66 f-250 stepside, im sure the truck had a 390 in it but i havve know idea what happend to it