Like mentioned above, stock bolts are Torque To Yield. So they stretch and are technically a one time use.
Some re-use them and no problems, others... not so much. Personally, I'd replace the bolts since they are cheap. Also, possibly a bent push-rod or bad lifter? Pull the push rod out, and roll it on an extremely flat surface, like your counter-top. See if it rolls straight. You could also swap pushrods and see of the "Wingle" follows.
Check for odd wear marks too. If you wanted to go the whole 9-yards, buy some Ls7 lifters (Fairly cheap these days), and replace your stock lifters with those, to eliminate the possibility of it being a "deflated" lifter.
