I bought a 1975 Chevy Scottsdale truck that is supposed to have a 427 (crate motor from the dealer) in it. I've checked the serial numbers and the exhaust manifolds say 454 police, the front of the block (timing cover) says 1973-1975 454 and the intake says 66-69 427.

So is it a 454 block with 427 pistons etc. or a 454 with a 427 intake? Can I tell what I have without taking the engine apart? Does it make a difference?  

A 454 has an 8in. balancer with a counterweight inside. The flexplate or flywheel is also counterweighted. Pull off the access cover for the flywheel, and look for a weight welded to it. If no weight, then it is a 427. Both would use the same exhaust manifolds,timing cover and intake manifold. 427 and 454 blocks are the same except, sometimes the 427 block wasnt clearanced for the 454 rotating assembly. The bore for both engines measures 4.250. The difference is the 3.375 stroke of the 427, and 4.00, for the 454. By the way, that is a really cool truck. Is it in nice shape?  

Thanks for the input. Yes it is a very nice truck. The paint is awesome, it has a lot of diamond plate 'accents', the interior needs work though.