360 or 390 Big Block

How can I tell if I have a 360 or a 390? The rating plate has been removed prior to purchase. I have a 1974 Ford F350 Super Camper Special and this might not be the original motor. I know for sure that it is a big block 360 or 390. If anyone has any info please let me know. Thanks

Umm find someone that has a cubic inch tester and test it but i honestly dont know of any other methos im not to familiar with those motors but if they have differant firing orders u could check that b/c just about every ford motor has a differant firing order.

I would get the engineering numbers that are cast into the cyl' heads and also the intake and compare them with a known true 390 cid 1974 ford truck. Ford made quite a few 2wd 360 cid f250 and f350 pickups. Most of the 4wd 250/350 were 390 cid. Dont axe me why! I believe the only real difference was connecting rod length. Just as ford used a few different parts to create the 428 and 428cj, which were also based on the same block achitecture. Hope that helps you out.