I feel your pain. I've been working on my '57 Chevy Cameo kit and have been fighting with trying to build a custom firewall to accommodate the frame and engine off the Foose FD-100 kit.

I do know the cab and bed will fit on the frame with a little trimming on the frame. I've since put it away for another day to deal with it.

It's normal to lose a bit of mojo in this hobby.