Oldsub, I think you're right. IIRC, my junkyard TH350 was a "dual pattern", which meant it had two pairs of top holes. The lower & middle hole pairs are the same between Chev-V8 and BOP patterns.
mv


46 Chev One Ton Panel - S10 Frame Project

"What if the Hokey-Pokey is REALLY what it's all about?" - J. Buffet