Reposting here as suggested.

I'm rebuilding a 1990 305 TPI engine, right now it head-less so I can port and polish them. The crank is at 0* TDC #1 piston all the way to the top. I installed the a new timing chain, put the timing cover on. When I went to install the new hamonic balancer I noticed something wrong right away. The timing line on the balancer was in the middle. My old one(balancer) lines up pefectly with the timing cover. The timing marks are on the right hand side of the cover, so it's at the 2 o'clock position.

The parts store guy said I was running a 350 balancer on a 305. It is skinnier than the 305's. The engine ran good, no engine vibrations.

Should I recheck my timing chain and why is the balancer different on a 305 when everything but the pistons are interchageable?

It's not a 305 vs. 350 thing, it's where the timing tab was mounted. Some are at 12 o'clock, some are closer to 2 o'clock. The latter is the more common. The 2 o'clock type are easily identified because the timing mark is close to lining up with the keyway in the hub.

My '86 LG4 had the 12 o'clock timing tab, the '87 LB9 parts engine I bought had the 2 o'clock tab. Both are 305's, by the way. When I put in the 350 shortblock, I bought a new damper and used the LB9 timing cover to get the proper timing tab alignment.

Thanks five7kid, so basically just buy a new one like my old one. I though it had something more to do about the weighting system.

There have been all sorts of discussions about the damper needing to be designed for your displacement. Personally, I don't buy it. But, the easiest solution is to buy a replacement for your application.

You could get a bolt-one timing tab for the 2 o'clock position.