I have 5 gallons of sae 50 oil, not sure if I can run it in my 91 351. Advice for or against would be awesome, thanks

 

No. Sell that stuff to someone who needs it.

 

Against!

It'll take some time before it ever makes it way to the bearings and just stresses the oil pump.
If I were to use it, it would only be a quart substituted for regular multigrade in the warmer months.

Just my thoughts..

 

It could be usable, if you live somewhere it never drops below 80f, and your engine is loose enough that you run something like 20w50 anyways. Otherwise I wouldnt bother.