I'm in the process of putting together a Starion G54B Turbo motor and have three cams available from different engines that I could use for it. One is an original cam from a 1986 Starion turbo (verified by the letter 'A' on the rear end of the cam, per the 1986 FSM), one is likely an original 1988 Starion cam (FSM doesn't give any ID but gives the cam specs), and the third could be from anything, even aftermarket. Is there any way to identify the third cam by it's markings? I'm assuming that there is a difference between turbo and non-turbo cams, and guessing that there may have been different cams in the engines depending on what vehicle they originally came in (other than the obvious roller/non-roller valvetrain). If there's a benefit to using one of these cams over the others, I'd love to hear about it.

From about 85 on, at least, and maybe earlier, the turbo and carb cams were the same. There is a real advantage in the roller cams, though. Don't have a clue on your third cam, but you might try examining them side by side.

The '88 FSM gives the cam duration (264 degrees) as well as the opening and closing points, so I could throw a degree wheel and a dial indicator on the 88? and mystery cams and see if they both match the factory specs, but I was hoping for something a little easier.

I'd first try just setting them in the same orientation on the bench and eyeballing, and measure the cam lobe height with calipers.

I never looked up the 84 cam spec, but I bet it's in the fsm for that model. I did look it up in the 88 starquest manual and the 85 pickup manual and the 87 Montero manual, all the same duration and open/close specs.