I need some help identifing my heads and block. The castings on the block include 3916323 hi-perf truck pass and the pistons are domed. The heads have 3919840 gm3t hi-perf,i don't think the two were ment to be together but that is how i recieved them. Can anyone help me find out what these could have come out of?

The block is a early 68 396 block. The heads are more than likely 396 also depending on what they came out of. If there are some #s and letters stamped on the front of the right side deck of the block, that will tell you what it came from.

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67 Camaro SS Conv.
70 Challenger R/T Conv.