Having no luck - 67 barracuda Hedman Hedders

I am trying to install my new magnum 408 with Hedman long tube headers. car is a 67 barracuda, manual steering, manual brakes, manual trans. I have no clearance issues with them but i cannot get them installed. I tried putting the engine and trans in with the headers loose in the engine bay, no luck. My only problem is the passenger side header, It will not let the trans past. I can get the engine itself in and everything can bolt up but i cant get the trans and bell housing up high enough in the trans tunnel to bolt it in that way. I will try to bash the flange in the trans tunnel to allow the bell housing to move higher. Am i doing something wrong? Is there an obvious better way to go about this?