1966 Plymouth Barracuda Help!

First off, it looks like you are trying to use socket type plug wires on a HEI style cap. This won't work well if at all. What is the voltage at the coil?

As for the overheating, it also appears to have a "flex fan". These are notorious for maximum noise with minimum cooling. But so long as you are going over 35 MPH or so, the fan really doesn't matter.

Get it running and set the timing to something reasonable (10-12 BTDC) and then troubleshoot the cooling system.