1954 trucks with Hydra-Matic transmissions had mechanical (solid) lifters.

1954 passenger cars with Powerglide transmissions had hydraulic lifters.

Post the block casting number or the engine serial number (in the ledge to the rear of where the distributor goes into the block) and if it is a 1954 truck block, it had mechanical lifters. The best way to check out the lifters is to do what Stuart suggested (or, pull the side cover and take a look as you adjust the valves).