I believe one of the selling points of Doug Thorley headers is the fact that they will work with straight or angle plug heads. I have angle plug heads and use hooker super comps (which say they WON'T fit angle plug heads.........I even use regular length plugs not shorties, but I HAVE to run 90* plug wires). I believe on the site, they say that they will fit angle plug heads.
Give them a call, I'm sure they will verify this.