header fitment issues

[chevelleshack]

Hello , all . I am working on a 69 mustang with a 351w , edelbrock rpm heads & c-6 transmission . My problem is i have tried two different long tube headers , hooker competition & patriot , & both hit the floor on both driver & passenger sides & there is no way the collectors can bolt up without major cutting & reshaping of the collector or floor . Have also raised & lowered engine to see if different motor mounts would help but it did not . Anyone else have this kind of problem ? Thanks for the help !
Phil