checked the block numbers from old book and said was 350 roller block from truck with one piece seal 84-86? the crank is not in it were these internally or externally balanced? how can i check with out the crank???] i dont have the numbers on me now from the block

The key is that it is a one-piece rear main seal. That means it uses a flywheel or flexplate with a weight attached, making it externally balanced.

However...

The harmonic damper is NOT an externally balanced piece for that engine! Use a normal internally balanced part on the front end.

This is a little confusing, because the 400 SBC was externally balanced on both the harmonic damper and flywheel/flexplate because of the long stroke. In 350 and smaller engines, though, the two-piece rear main seal design crank had a counterweight cast into it external to the seal. When they went to the one-piece design, they couldn't put that counterweight there anymore, so they put it on the flywheel/flexplate. The good news is that a two-piece rear main seal flywheel/flexplate will not bolt to a one-piece crank.

I'm a little suspecious of the data you have, though. The one-piece rear main seal came out in 1986. Roller lifters came out in 1987.

ill have to get the numbers again

but it did have 4 bolt mains a one piece seal
and the provisions for a spider thing that holds the roller lifters

it was sitting next to a flat tappet block so the diff was clear

Sounds like an '87-later block, which means it is also one-piece.

The rear main cap and the back of the block will also look different between the two. The one-piece seal is held by a seperate aluminum holder, while the two-piece seal is held in by the rear main bearing cap & block.