Brian, are you talking the tubs or the rear tailpan/corner post area?
The tubs I trimmed to fit the existing quarters (which have been replaced by some hack in the past) I tacked them in multiple spots then used seam sealer to fill in the seams....
The corner posts I cut up higher than stock, as I was raising my floor 2" to accomodate the larger fuel tank. If you need to cut up higher into the box corners you could cut to good metal, then piece in a new corner to get back down to stock floor height and tie in a new tail pan piece.
Here is the inside of the box corner with the new tailpan coming into it...be sure to leave an opening big enough to get your tailights through...

And a hole for the wiring to go through...

these are the body mounts I made for the rear tailpan....a little custom for my application of raised floor, but should be adaptable to stock as well...

The tubs I trimmed to fit the existing quarters (which have been replaced by some hack in the past) I tacked them in multiple spots then used seam sealer to fill in the seams....
The corner posts I cut up higher than stock, as I was raising my floor 2" to accomodate the larger fuel tank. If you need to cut up higher into the box corners you could cut to good metal, then piece in a new corner to get back down to stock floor height and tie in a new tail pan piece.
Here is the inside of the box corner with the new tailpan coming into it...be sure to leave an opening big enough to get your tailights through...
And a hole for the wiring to go through...
these are the body mounts I made for the rear tailpan....a little custom for my application of raised floor, but should be adaptable to stock as well...

