Header question

[RaycerX73c20]

I used the search but cant find what i looking for. Well we did the motor swap this weekend. Yanked the 454 out of the truck we are getting for the swap and installed the 383 from the other truck. 454 with everything dropped into the other truck with no problems. the 383 into our truck ran into issues with the headers. We cant mount them. they hit up against the K member. They fit fine in the other truck with the 383 but not in ours. Is there a difference in the engine bay k member in a truck that originally came with a big block and one that came with a small block? Both trucks are 4x4s The other truck is a 73 k20 ours is a 74k20 on a unknown year K30 frame. The other truck was gone when we started on ours so i have nothing to compare with. the headers are not full length headers or at least they look like a mid length type. They are made by Headman.  Any ideas?

[Irish_Alley]

the k30 frame is going to be thicker so i would think they would have diffrent cross members how bad is it hitting could you heat up the header and bend it a little I've heard of problems with getting them to fit even on a 1/2 ton truck due to the cross member

[fitz]

 It could be a problem with the motor mounts. While the big block will bolt up to the stock small block mounts that are bolted to the frame there is a height difference between the two.

[Torque454]

Ida left the big block in there But yes there are different holes in the mount mount brackets on the frame, maybe you have to move the mounts higher or lower?

[RaycerX73c20]

the k30 frame is going to be thicker so i would think they would have diffrent cross members how bad is it hitting could you heat up the header and bend it a little I've heard of problems with getting them to fit even on a 1/2 ton truck due to the cross member

From the position I can see I need a 1/4 to 1/2 inch