Howdy. FWIW, I recently rebuilt my 67" Firebird 400/4-speed. Stock manifold exhausts, no headers. I discovered that aftermarket pan that I ordered from Butler Performance, which was supposedly was a stock replacement, has too gradual of a slope from the front to the back of the pan and as a result the inner right tie rod (with zerk at end) rubs against the front passenger side corner of the pan when I make hard right turns. This rubbing caused a crack in my pan and I lost 2 to 3 quarts of oil within a few minutes! Measure the clearance you have between your suspension and tie rod and ensure that you have sufficient clearance. I am still looking for a stock replacement pan that can fit. y clearance issue could be due to a combination of factors such as change in position of the block due to new motor mounts, or a tie rod joint and zerk that is pointing in the wrong direction, but I have read other customers reviews of oil pan replacements and the clearance issues.