The wiring harness was already made up by Stein for the 9A project that I bought. It has the plug for the GMC 305. Is the GMC 507 a "direct replacement" for the 305 without any mods to the plug?
It?s a different physical size, but the GMC307 would be a direct replacement for the GMC305. No sense in going with a GMC507 over a GMC307 if you are already wired for a GMC305/7.