The fuse for the turn signals keeps blowing. I have no idea why. New dash harness, used the fairly new headlight harness all other harnesses are new and in good condition. All bulbs are good. Is it possible that even though the wiring insullation wasn't damaged at the bulkhead connector; the connector was slightly damaged from the fire. Could the temp have damaged the wire on the inside enough to cause additional resistance. The fire was primarily on the pass rear side of the eng compartment.

Does it blow when you use the switch, as soon as you put the fuse in, or during some other change (turning the wheel, bumps, other accessories on?

Normally, blowing a fuse means the circuit is shorted to ground somewhere. Adding resistance (bad connection) will cause the lights to flash slower, not blow the fuse.

Try removing all bulbs (inspect the sockets), and try again. If it still blows, it's the wiring or switch. If it doesn't install the bulbs one at a time, checking each time. This should help narrow down the circuit. You can also disconnect sub-harnesses.