I was finally able to find and read the BOM numbers for the axles from the beater Bronco II; I wish I had found them earlier because it would have saved me some headache
The front was 603394-5 and came back as a '73 F100/F150 Dana 44 with 4.09 gears and an open carrier which I had figured out the hard way already. The rear axle was the real mystery since it had 3.5" tubes 9/16" lug nuts with left hand threads and a really heavy-looking center section casting with a non-machined boss for an ABS sensor, but a Dana 60-sized cover. The BOM for that axle was 605212-5 which came back as a 1984-85 E-350 Van SRW Full Float Dana 61 with a 4.10 open carrier. Apparently Dana 61s came with the stronger housings and large-bore spindles unlike standard Dana 60 full float rears, but the pinion is further offset than a regular Dana 60 (in order to accommodate 3.07 gear sets regular Dana 60s can't run) which means 4.10s are as deep as you can go without getting janky with spacers and non-standard bearing races. I had already been keeping my eyes open for a '99+ E350 full float Dana 60U, but I guess I really need to find one now.
For anyone else having trouble finding Dana BOM numbers, both of them were on the passenger-side axle tubes on the side with the cover. The numbers were only about 1/8" tall and not stamped very deeply into the tube which makes them really hard to see with paint, dirt, and/or rust on the tubes.
Dana 44 BOM about 2" to the left of the casting
Dana 61 BOM location
Before cutting the front axle housing, I measured the length fo the tubes from the ID with my best tape measure a few times. I hooked the end of the tape on the edge of the tube where it was pressed into the center section next to the carrier bearings and measured to the edge of the ID where the tube was pressed into the "C"s. Then I cut it up and left ~2.75" stubs of the original axle tube sticking out from the differential casting and "C"s to give me plenty of material to make plug welds and to help keep everything straight with the new tube sleeved over it.
The original tubing turned out to not be particularly round and was worst around the center section casting. It seems like whatever tooling Dana Spicer used to press the tubes and assemble the housings caused a bit of deformation creating an interference fit with the ID of the new DOM tubing. I used a sanding drum to take down the high spots and did a lot of test fitting with the DOM tubing to create a snug slip fit. I didn't need to remove a lot of material, but I took my time to avoid taking too much material off.
Then I rough-cut the new DOM tubing to length accounting for the change in inner shaft length by adding and subtracting the difference from my original measurements before cutting the housing. Then I sleeved the rough-cut tubes onto the housing and measured the distance from where the original tube was pressed into the center section to the edge of the ID where it pressed into the "C"s to determine the final amount to turn the DOM tubes down. Afterwards, I chucked the DOM up in a friend's lathe to turn them down to length, square the faces, and bevel the edges for welding. While I was over at that same friend's shop, I put the tubes up on his mill to drill the plug weld holes instead of trying to do it on my crappy Harbor Freight bench-top drill press ;D Proper machine tools are really nice; one day I'll be able to equip my shop with some real equipment
I also got the body tub back from the blaster's. It looks much better without the rattle-can camo job
Unfortunately, the blasting revealed a few more cancer areas that will need to be addressed.
. Randy had diamond cut plate reinforcements in that area, wish I would’ve. 
