Discovered that my 1971 302 has a 5/16 oil pump drive shaft rather than a 1/4. This is making my distributor meant for a 1/4 impossible to install. Thoughts? I am kind of a dead end here and want my truck running badly.

 

Not sure how that's possible. Was there a distributor in it before?

You could try installing a 351 distributor.

Otherwise, you would need to install the correct oil pump and drive shaft.

 

Pics of your motor? I think you have a 351 there.

 

Someone would have had to change the oil pump, distributor and shaft to parts from a 351W for that to happen.