[Dominik]

"the quote was $18K"

This is quite a quote...

As for the measurement in an early picture showing the length incorrect for the main rail, I have 2 points you may want to consider:
Is your tape measure correct?
And the variation might actually be within ISO tolerances for welding.

I try to see if your front shock tower is twisted because for me it merely looks like the gusset sits at an angle, which has no detrimental effect on the mounting. To be honest, by looking at the picture I can't tell.

I admit, the gap from control arm mount to chassis bracket is too big, but can't this be shimmed out? Well, not anymore...

I agree, the body doesn't fit. But that may have been the radiator frame off a bit, and/or the boot frame. The 4000 body on a 3000 frame is not an easy fit. Not even a 4000 on 4000...

I tried to see it from your angle, but I am biased because I once was building from scratch myself.