A 2 and a half truck ton called a deuce and a half really is an M series thing, They were jimmys as a cckw, so the cckw would not be an answer for his question, to be a putts, but will add they started out gassers and went to multis , then an upgraded multi for a few reasons, but not because the 427s were worthless , actually they were and are runners for sure. and they were solid, they did have a head gasket problem that they had problems with mostly in theater. under the condions of vietnam to be more on it, and even the 465s had an up graded version of the head gasket, so the answer is if U find a gasser it has probably been in private hands a long time, and the upgraded trucks were done through out there life, the 465 is very close to exactly a 427 ......a little more bore is really about it, and to bolt one in is only different in the front cross member, the 427 has 2 tabs like the gassers, and the 465s got an upgraded cross member and the bolt holes are cast into the block, the rest of the motor most people would have to read the tag to know the difference....Now the A 3 is a diesel , but I usually do not include them, but they should be they are the last upgrade a very awesome and historic truck ever got,