Geoff Weeks

Engine is obviously a replacement/reman, but that does help with axle ratio, unless those also have been replaced.

Likely a Big Cam 3, Could possibly be a Small Cam Magnum, I can't see enough of the cam follower covers to know. Would be nice to know axle and ratio. Talk about rode hard and put up wet. A little cleaning would make it sell better.

255 70 22.5 is the smallest you'll be able to fit to what you have there now, Will be smaller than the 9.00x 20s'. I'd still check before I assume. Loaded will make a difference.

Check the clearance 1st. The tires you have on there now are equal to lo-pro 22.5 in diameter, if it hits now, then really the only choice is 17.5 which take a different brake set-up (12.25 x 8 drum) S cam and bracket. Most cases you can't just swap hub and brake spider, as the spider is welded on. Going off road, you know those axles are going to have to pivot to the extreme going over rough ground. Better to know now rather than do the work and get stuck or tear up tires. I've not see a early low boy like that with anything other than 15" hubs (which will take 17.5 tubeless "adapters") Set up with new axle and hub pilot 17.5's would make that a good trailer if the rest isn't all cracked and scab welded.

Those look like 20" rubber not the 15 that most lowboy's from that era had. 9.00x 20, You can mount tubeless demountables on there 295-75-22.5 would be the same OD or you could go smaller 255's which would lower the deck height a bit. I think I'd start by assessing what is there, and how well it is done. If the axles are installed in alignment with the king pin, I wouldn't change. If it was scabbed in and everything is out of alignment, then you are going to have to cut it out to align anyway. Alignment is done by how the brackets are welded on. Everything will be "floppy" until welded, and you better get it right. One looks to be "Propar" axle and one looks to be a axle where the spindle is smaller for the outer bearing. One thing I see in the latest picture that concerns me: Will the tires clear when the suspension is tilted to either extreme? It looks like they will hit when the rear is compressed fully and the front might hit when it is compressed fully. Better to find that out now, rather then after you do all the work. It wouldn't surprise me to learn it had 15" hubs on it from the get go, and someone changed without checking clearances. New axles with 12" brakes and 17.5 tires would be the modern equivalent. I did one axle job on a trailer, measure 4-5 times and weld once!

1st, it looks like they are 12" brakes so new axles will also need to be "low boy" axles, 2nd that is a lot of brackety to weld in for no gain. What is wrong with the current axle? Axle and brake are two different things. That may be an SR-5 but I can't tell from the picture. What size tires does it have on it now?

Coupla things, screw clamps on rubber air lines are not permitted. No way "one is fed from service the other from supply". You've got to get what you have legal before trying to add spring brakes. Without seeing the whole air system, I can't tell what is buggered up and what if anything is correct. What I can see from that one picture will get you shut down in a heartbeat. You've got kinked copper line. I would correct the defects that will get you shut down. I towed many trailers without spring brakes (I was a heavy hauler) over the years. Once the system is correct, you can see if there is enough room to add what is needed for spring brakes. Also need to correct what is wrong with the RH S cam bracket, the push rod is not inline with the slack adjuster. It looks like something with the slack adjuster bushing isn't right, preventing the can as push rod from being properly in line. everytime I look I see more wrong, right chamber fully extended, left chamber fully retracted, what the heck is going on there? Stuck or air to one chamber only?

Heavy equipment trailers were exempt from the spring brake requirement and may be still are. You need to plumb it correctly with an SR-5 valve not just with a relay valve. Look at Bendix's air brake manual for the correct plumbing or leave as is a carry some chalk blocks.

I have a truck with 30 forward gear possibilities. 13 at best are useful. Nothing cool about ratios that for all purposes are the same. No "show-off" potential because it will just sound like you stepped on the clutch and off with no change in engine speed if the gears are overlapping. Map out what the ratios would be in each position and how the rpm would change. In my case with a plumbing change I could add 5 more useless selections! With less than 1/2 the available selections being of any use, adding 5 more wouldn't change that one bit.

Kinda sounds like it was "finding ground" through the ECM circuits?

I was talking about the GMC/Chevy using them, I know they were in other trucks and have seen one (in a D/R) at the ATHS show IIRC.

Steel cable is used on rail cars. I have used chain, but they discourage it claiming it "damages the sticks". rubber belting or steel edge protectors do a good job.

Yep, looks like the docks at the plywood plant east of Bemidji MN or several in (now closed) fire brick plants in MO.

Seams like those docks were made for railcar unloading. Been in a few like that. I was delivering a "drop table" to a railyard (drops the motors and axles out from under the locomotive) . They were insisting that I back in an 11' door when the load was close to 14" wide! Ended up on the old turntable and backed in on the tracks. Drove onto the turntable then rotated and back into the shop.

For the right load, they are the best. Moving production machinery from one plant to another, that can't get wet, there is no equal. On the other hand, general flat bed freight they are a mixed bag. When conastoga's first came out, there were states where the width was a problem on 102" width trailers. It took federal ruling that the tarp system wasn't considered the trailer and could be wider.