ATF and acetone is the best rust buster,but we used Marvel Mystery Oil at the junkyard most often,on an engine we were trying to save for an antique that was rare..we had plenty of used ATF,but acetone is like 17 bucks a gallon,so we were unwilling to invest that much on what might turn out to be a junk engine,so we often just used ATF and maybe some gas to thin it out,or diesel fuel,on other engines that sat,and customers wanted to see if they would run before buying..
..(This was back in the '90's when a gallon of Marvel was under 10 bucks--not so today,its closer to 20 !)..
You can make a oil pump drive adapter from a large screwdriver and a piece of pipe or tubing the right size so you can spin the oil pump with an electric drill,or grind off the teeth on an old distributor's gear..
I would wait till you get it to run awhile ,then see if the plugs are oily--the rings may be stuck and it can take quite some time to free them up (if they free up period)...old chevy small blocks often have valve stem seals dissapear and that lets oil drip thru the guides when it sits ,and the next time it is started up the oil cakes onto the plugs..
We often had engines that we freed up smoke like a tire fire for as long as an hour or more,we had to keep topping off the oil--many stopped smoking eventually, and didn't need any internal work..others got worse,and started making scary rapping or ticking noises,those were sold as
rebuildable cores".