Finally got the box mounted and this how-to is a wrap. Luckily all my measurements worked out and it sat right and holes lined up fine.
Here is the underside showing some of the standoffs and extra brace.
I used regular 1/2" carrriage bolts, not anything vehicle specific. They look great and you'd never know they were moved.
And here is the truck.
1974 F250 4x4 CCSB, 460 Swap, 4 Speed
1988 F350 4x4 CCLB, 7.3 IDI, ZF5 Swap, 4" Lift