CV- F100 Frame Question

[Paintman77]

Hey guys. I’m getting everything mocked up for a CV swap. My truck was originally a 360 LWB 68’. Once I started the mock up and removed the front crossmember I noticed some severe cracks in the frame. I found a nice short wheelbase frame local for a good price so I decided to continue the plan using this frame instead. When I cut my crossmember out of the long bed frame the crossmember was double walled like I’ve seen in several other builds. When I removed the crossmember from the new frame it was single walled. Is there an explanation for this. SWB was a 70-72 302 truck I think!?! Trying to load pictures but files are too large from my phone. I wasn’t sure if Ford used different crossmember for different engine. I’m not sure why they would or do I have an earlier model frame.

[Fordkid68]

I don't know. I never heard of ford making two different cross-members, but maybe it is because it's a later truck. It would definitely be interesting to find out.