Steve
Truck engines generally have a taller deck. You can check by measuring the distance from where the water pump mounts to the top of the block or look at the left water pump mounting point and see if it is solid or not. The 402 is nothing more than a .030 over 396. Nothing wrong with that block to build up, hell the first 454 I built for my 70 was out of a boat. If anything you could probably bump up the compression by means of the pistons, shave the heads a little, and have a nice little rat motor that can run great on pump gas.
Tom
70 Chevelle SS
