I also have ceramic Hooker Super Comps on my '68, but had to dimple a pipe at the steering box. Plug wire clearance is no problem with my angled plugs. I've run Cyclone, Hedman and others with no problem. Tube size seems to be the critical issue--once you get past 1-5/8" it seems to get dicey. My present Hookers are 1-3/4"--what size are yours, 68Z? For my money, I'd buy Hedman if I had to do it over again. They were 1-3/4" tubes and built heavy and solid with no clearance issues at all. They're collecting rust right now because I wanted ceramic-coated headers this time around. The ceramic coating is terrific and worth the extra $$! I was disappointed that the Hookers didn't fit perfectly for the money I spent on them. My 2 cents.