Overheating issues on a rebuilt 360

I’ve seen this but when you mention timing you mean On the distributor or on the crankshaft pulley?
Well you turn the timing by the distributor and check it by the crankshaft pulley...
get it started and running and up to two grand and then turn the distributor a little bit left and a little bit right and look for the highest RPM... You should hear it no problem.. then verify with your timing light on the pulley or the harmonic balancer actually..