518,46RH,46RE
If you have / friend/ etc with a running magnum setup, you could find out with not too much work. I built a simple redneck backyard adapter to get a carb mounted on top of the EFI manifold to "test fire" an engine. You could leave everything in place and block the fuel, or even re-route the fuel to a regulator for the carb
This thread:
LMFAO Anybody figure out what this is?
Note that photo is before I swapped the dist. this is a completely non-EFI test
I built this to adapt an AFB to the EFI manifold, front barrels only