You now have a nice, clean engine. By now, most of the gas in the engine has probably evaporated, leaving nothing to lube the bearings on initial startup. You have two choices: either cross your fingers and start it up, or try to pre-lube it. If it was my tractor, I'd just fire it up. The few seconds without lubrication aren't going to be significant compared to the 60 years of use your tractor has seen.
If you want to go the pre-lube route, I think you can remove the distributor, then make a shaft with an end shaped like the end of the distributor shaft. Then insert your homemade shaft through the distributor hole into the oil pump and spin the oil pump using an electric drill. Once you have oil pressure, the engine is lubed. I've done this with other engines, but not with a Ford 172; I assume it will work.
A compromise between pre-lubing and "fire her up" is to pull the coil wire and crank the engine with the starter until you have oil pressure.