The problem is, there is a lot of different ways to get where you are trying to go. The answer to heads, pistons, and cam will really come down to what you are wanting to do with the truck and what condition it is in now. It looks like you at least have a block... looks like Mark IV? Did you get an entire rotating assembly and heads with it too? If so, what heads? What's your budget?
If you got a complete engine, and you are planning on just having a mild street/truck/towing type engine... I would suggest just getting the heads you have now rebuilt. Even basic iron aftermarket heads will run you $1,000/ea. I had my stock L29 heads completely redone with cleaning, new guides installed, guides clearanced to allow more valve lift, machined for positive lock viton seals, basic valve job, rotator eliminators installed and new springs/retainers installed and spring pressures checked for $600 total.
If the block is in good shape and doesn't need to be bored over, you can just keep your stock pistons and get a hone and new rings. If you need them bored, you can get the proper pistons to get a good compression ratio with the cylinder heads you have. Usually the older truck 454's will have really low compression. Bumping it up to 9-9.5:1 will really help the power and drivability.
Cam should be chosen based on the previous engine internal choices and the expected use case. Just call the cam company of choice and let them know what you have and what you expect to be doing with the truck. They will recommend a good cam for you.