Which way did you bolt the rod caps up, bearing notches on the same side or opposite. Rods and caps are made as a matched pair and the caps are only fitted one way. V8 rods that run side by side have chamfers to clear the radius ground into each side of the journal. If you reverse the caps then they will not clear the side of the crank, locking up.
Did you turn it over by hand before you fitted the sump.
Most important thing is to double -check as you go, and when pulling rod caps off, mark them so reassembly is easy.
This thing has nearly beaten you so maybe you should walk away for a while, write down what you need to do to make a good engine and go from there.
Experience is going to be your teacher here.
You may be able to reuse your head gaskets if you have not started it this time.