I am thinking cap, rotor, plugs, and maybe wires; however, it runs smooth as can be while it goes down the road. It only idles rough. I am not sure if it is missing yet, but I can't feel a miss while I'm driving at all.

Wondering where to begin...

What year is it? our 95 does the same thing, been chasing it for a while.

It is a 1998. Pickup has 240K on it but the motor has 80K. I just bought it, so I don't know what they all replaced during the overhaul.

Could be an intake leak,do the old 3 foot hose to ear trick

Could be an intake leak,do the old 3 foot hose to ear trick

Never heard of this trick. Explain.

Start with the wires. I had an MSD 6A ignition box on my 97 and it would eat OEM wires. They'd be carbon tracked everywhere. Be careful replacing them... you'll bust the hell out of your knuckles getting the wires off of the cap and getting the OEM cable looms open.

Pull your EGR valve off and clean it. Also get a can of carb cleaner and with the truck running spray around the intake. That is the best way to check for leaks. If you have one the RPM' will change. It would also help to know what year we are dealing with.

take 3 or 4 foot of fuel line and put one end to your ear and run the other end around the intake. If there is a leak it will sound like a tire going flat (nail hole).

Also, if the throttle body is original, check for wear in the throttle shaft, also the idle air control motor might be bad as well. Also in the throttle bore itself. There could be wear in there where the throttle blade rubs on the housing. Also check for other vacuum leaks not mentioned above. cap, plugs, wires, rotor, are all good places to start as well. How old is the dist itself? I pulled one out of a Vortec 350 with 100k and it had some pretty good slop in it already. Could cause some issues.

Vortec 454's known for leaking injectors also...

I got a pretty good deal on this pickup. I just hope it doesn't turn into a money pit.