I looked up bulkhead connectors at Evan's and they don't sell E-body ones.....just A,B and C-body) M&H has an exclusive contract with Year One. Anyone else selling their harnesses is buying them from Year One and reselling them. I don't think Evan's offers "main dash harnesses". You'll have to buy one from Year One if you are going to replace the entire thing. Hopefully you can find a used harness that still has a good bulkhead connector. The other "option" is to see if there is a good unused slot in the connector and move that wire to a different place. You could also just bypass the connector and run a new wire straight through.
