The Stovebolt Site Forums The Shop Area Engine Shop Stupid mistake

http://freezeplugfactory.com/expansion-plug-size-chart/

http://www.dormanproducts.com/catalog/hardware2006/127-130_Sec8_Part1.pdf

Get the Dorman number and go to any local parts house, they should be able to order one for a few dollars or less. You want the concave expansion type.

Here is a list for your engine, http://freezeplugfactory.com/chevrolet-constants/ scroll down to 235, you want the 1 5/8" block, concave
Joe