Back in '67 it ran good in my '63 Plymouth Valiant. I always had to leave Dad a note " Boat needs gas". Once I forgot. Not fun paddling on the Coosa. At least it was down stream to the ramp.
It's not the oil that will hurt it, it's the fact that it's so old. But, as stated above if you use it a little at a time you shouldn't have any problems. I'd put a few gallons in after every fill up.
but it will smoke.