You may have ruined the motor (temporarily) as some have pointed out.
So what? If you’re restoring the car, rebuild the engine (or have it done). It will be a better engine than it ever was if you do it right. Materials science, fabrication and machining have come a long way since 1970 (and that car was actually assembled in early 1969 from 1968 parts, of course.)
Anyway, I don’t recommend trying to diagnose and repair it. Write the engine off and rebuild it. If you got sand in the block you will have buggered the main bearings. Big deal, get a billet crank. If you didn’t get sand in the block then you probably got water in it, which you’ll find out when you check the oil. Regular water in oil sometimes just looks like beads, but you’ve probably got “peanut butter” in the block (water mixed with engine oil at high temperature makes a gross emulsion.)
There’s also bad things that could have happened in the head, but again, who cares? At minimum you will want to do a head job, and install hardened valve seats (and better valves while you are at it) so that the engine will run on unleaded fuel.
By the way, if you ran the engine on unleaded fuel, then yes it’s normal for it to run unusually hot. Check the oil and the coolant anyway, and don’t run the engine any more. Tear it down and make it super. Have fun!