Does anyone have a Demon skeleton laying around?

I'm sure you know that screenshot you took above is for horizontal dimensions, not vertical dimensions..

But anyway, just for information's sake, since you're saying the wheels have nothing to do with anything in that diagram, lets just delete them from the diagram... Then where is the O-line?

I literally circled the vertical dimensions in red on the diagram I posted before. I’ll post it again
IMG_0159.png


The 0-line is exactly in that same place. 3.94” below the center of the rear shackle mount, 5.98” above the bottom of the front frame rail at the torsion bar crossmember measuring point, 1.24” above the rear K member bolt and 1.82” above the front K member bolt.

Yeah, I know, your car doesn’t have those 3 front points. But it doesn’t matter!!! If your car is on a level slab, you measure down from the rear shackle hanger to the floor. Let’s say you put your car 3’ in the air (this is an arbitrary number!). So it’s 36” to the O line, so the center of the shackle mount is at 39.94”. Now, you move forward. The 0 line is at 36”, the measuring point at the frame is 5.98” below that. So 36-5.98 and you need 30.02” from the floor to that measuring point. Now your crossmember is located, and you move forward and do the same process for the front rails at the K frame bolts.

But you’d need a flat and level surface to drop plumb lines to in order to measure that. But you can’t seriously do this work without that, or a frame table. And then you’d need to drop the plumb lines and measure the diagonals to get it straight.

This is chassis work 101. That project of yours is a BIG one, because of all the reference points you don’t have. It should really be on a frame table because of that.