The Melling M-45 pump fits all 235 and 261 engines
The M-45 is much shorter than what I pulled out so the rest of the system doesn't really fit if adapted to one. That said, I'd rather use whats correct.
GM 3701562 brings up the '53 corvette mostly, which is why I looked into it possibly being incorrect for the bigger 261.
Is there a "better" pump than the M-45 for the 261?