First of all, Stovebolts don't leak they just mark their spot!
Lots of good advice stated by others here.
Remember that todays oil is vastly better than in the 50's, the API specs. now allow less zink and that can cause more wear on flat tappets.
Without debating the weight of what you use try to select a product with enhanced lubrication.
There are a few oils designed for completion and various additives that can assist the lubrication in old engines.
Compression Ignition (diesel) oil has a higher zink content but is may not be best for SI (spark ignition) spec engines.
Just to annoy some folk I use Rotella synthetic 10W-40 diesel oil and a bit of Lucas supplement in almost everything. Our Volvo V-90(my daily driver) gets 5W-30
