Need some help from 13ft. 1981/82 BURRO owners

I'm finally making some headway on the off-trailer rehab of my 1981 13ft. Burro that I started a few years ago. I had some help from a few fellows who cut and installed a new floor into the shell but I'm having some difficulty in getting the shell positioned correctly on the trailer frame. I'd really appreciate any help you fellow Burro owners of the same size and vintage can give me in the following areas:
MEASUREMENTS-
1) How does the doorway line up with the open ends of the square tube frame supports that face you when you look underneath the doorway? (Right now I'm measuring about 2-1/4" from the surface on the tube closest to the doorway on the left TO the inner lip of the doorway.)
2) Where is the center of the axle hub in relation to the wheelwell?(Right now I'm sitting just about midline-underneath the "AR" of the WARNING label!)

FLOOR SUPPORTS-
By moving the shell/floor around to get it right on the trailer I've lost the overlap of the seams of the floor sections on top of the angle-iron cross-piece supports!
1) Can I safely drill holes into the vertical side of the cross-pieces to attach (with bolts) angle braces to support the (now unsupported) edges of the floor with out weakening the existing supports?
2) Should I just use several of the small angle braces for each edge or would you suggest adding supports going front-to-back between the existing cross-pieces?

Thanks in advance for your help . There is still much to be done but I'm optimistic and hope to be able to actually do some camping in the Burro this summer!

[MyronL]

So you've got this shell hovering over a new floor and need to know where to drop it down?? Just off the top of my head it seems most sensible to concentrate on centering the wheel well on the center point of the axle and assuming all is square from that point on to accept whatever other allignments result, adding bolts as needed. Seems to me the most critical need at this point would be to insure plenty of tire clearance in the well. Where the floor butts into the bottom of the door gets adjusted with a custom made threshold that mates to the base floor. That's what I did.

I also wouldn't use angle brackets. Why not drill directly into the cross members? Direct connections seems to me much stronger.

When I replaced extensive rotted flooring I used 5/8 thick plywood as the new floor base, but covered all resulting irregular seams with 1/4 inch thick plywood. I added 3/4 thick plywood on top of that only in the dinette area to insure a solid base for the table pedestal, which bridged over the 5/8 seam in the floor there. The resulting lip I deemed inconsequential.

Add your favorite flooring on top of that.