I keep forgetting that it’s an L-150, everything LARGE BY HUGE. I hope you can come across C50-C70 stuff as easily as I still can here ( even though the high scrap prices in ‘08 made everything the cleanest it’s been since World War II). I guess that’s at least a 1-1/2 ton rating? Check parts available by years, but I believe most C-60 is still serviceable through rock auto, even Napa. Big GM or Rockwell axles. An eighties GM based Thomas school bus will be your best friend, almost no demand for parts and steel Budd wheels too. Single speed axle ratios of 6.17 or 7.2:1. Most are C60/70 platforms. C60 enthusiasts page C60.com for tech. May be able to find something newer in the 10 lug pattern to get away from the Budd split rims, shoot for the cheapest tire availability. Most junkyards here use them for storage and office space, show up with a load of railroad ties from Lowe’s to put a couple of crib cages under each end and you can buy about anything you want, cheap if you make friends... If it were me, I’d cut the spring mounting bracket rivets and roll the whole mess home. When you get to a bare frame and everything cleaned up, whack all the rusted unserviceable springs, mounts etc. etc. and put them out to sale on Binder planet. May find someone that just has to have your old axles. If you go with a \6, do the Dutra split manifold kit (if you got room for the exits )and get an iron super 6 intake. I can’t remember the brand of \6 manifold gasket that comes up on here but use it too. All cast iron works best, and has the lowest maintenance on keeping everything tight and leak free in this heavy of an application. It’s going to pulling a lot of rpm and load at the same time, so the exhaust gas temps are going to be pretty high. Not that it matters a whole lot to a \6, I have mercilessly abused several and never broken one.