The F54X is, as you guessed, was originally designated for truck service. A '54 235, manufactured in the Flint, MI plant. So here's the thing. Through '55, the 235 blocks that came from the factory with solid lifter cams did not have the oil gallery drilled to support hydraulic lifters (all '56 and up blocks do have that oil gallery drilled, regardless of original service, but not the earlier blocks). Unless you find a machine shop that can affordably "rifle" drill that gallery, it's solid lifter camshaft and lifters, only, in that block.
But really, the options aren't all that expensive. A nice upgrade is the Elgin E-293-S cam, which is ground on new blanks to the 261 truck engine spec. It's the same cam grind that was used in the '53-'54 Corvette 235s, so slightly higher lift and longer duration than the 235 cams. Combine that with the truck aluminum timing gear and Melling JB-874 (or Sealed Power AT-874) lifters, and that's a very nice combination. The Elgin cam is available online for around $120, last I looked. HRL Jerry recommends a similar cam from another company, that's also an option... foggy memory on the details.
Hope that helps!
Doug
