[Vortec350S10]

well i guess see how easy you can dent in the area where they hit. if you get it banged in enough so they fit make enough clearance to allow for engine movement, at least 1/4 inch clearance. You can heat up the metal with a torch to soften it if there is nothing in the way to get burnt. it sounds like you got more trouble with your headers than i had fitting manifolds on my s10! and yours are made for that car! I wouldn't dent up the headers unless you absolutely can't dent the firewall enough. What brand are they anyways?