Based on what you have described, a teardown, thorough cleaning and evaluation of the internal components is the only truly reliable solution. The possibly 33 year old oil has, in all likelihood, solidified enough sludge in the bottom of the oil pan to at least partially clog the oil pump pickup screen and possibly the oil pump itself. The oil that is still liquid has been mixed with condensed water and has been circulated (however weakly) through the engine so the crank, rod and cam bearings will need replacing. The cylinder walls, at the very least, will need to be honed, and may need to be bored out. The piston rings will need replacing if honed and the pistons and rings if the cylinders are bored out. The rods and wrist pins should be evaluated. The lifters will need replacing and their block bores honed, and replacing the cam would be a good idea. New oil pump. All engine block oil passages, after removing the threaded pugs at their ends, need to be cleaned out with a gun cleaning rod with a copper or brass brush (my personal choice is .22 caliber). All freeze plugs should be replaced.The crank will have to be evaluated, including measurement, to see if it is reusable. The oil return passages in the heads will have to be cleared. By rights the stripped block should be hot tanked at a local machine shop and checked for any cracks that may not be visible to the naked eye. No mention has been made about the cooling system, but if the oil is that old, chances are the 33 year old coolant lost its effectiveness long ago and may have frozen in the block at some point, cracking it. Those cracks will widen as the engine warms and mix more contamination into the oil from coolant passages as well as possibly causing low compression and / or hydro-locking of the cylinders after the engine is shut off.
The cleaning process with such old oil and solidified sludge is not just a matter of clearing passages, but also insuring that there isn't any sludge left in recesses that are not easily visible. The new oil in a newly rebuilt engine (or any engine for that matter) can soften old sludge to the point that it will break away from the surface it was adhered to and travel through the engine, contaminating the new oil on the way and possibly causing new blockages depending on where it gets caught in the engine.
I really don't want to be the bearer of bad news, but in my opinion, any attempt of a less thorough repair at this point is a roll of the dice. Even if it were to run, however poorly, it won't be reliable and at some point, not so very far in the future, will fail, and in all likelihood will not be repairable.
