I'd consider the low risk option of
installing a GM NOS set of lifters.
These are very hard to find in decent
condition.
Here's a set on ebay.
photo at photobucket

http://i669.photobucket.com/albums/vv57/glp0329/spotting/GM5230650_zpsbdce634c.jpg

http://www.ebay.com/itm/321191571371?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

You can always send the seller a message
asking him if he'd take an offer.

George
in
New Jersey

1954 3600
A big help to many on the Bolt
Now cruising in
The Passing Lane