please post up any findings.
sorry for taking so long to get back to this thread, ive been busy. here's my 2 cents. this is based on memory, so please correct me if i'm wrong.
1. you said you got the 4-bolt box out of a 97 f250. since the 97 f250 is still OBS, i thought they only came with the 2-bolt. that would be really cool if you found a direct bolt in 4-bolt.
YES - 4 bolt from 97 250HD
2. both the 2-bolt and the 4-bolt use 5/16" threads on the pressure side, 3/8" threads on the return side. the only difference is the inverted flare vs o-ring. not sure where you're getting the 18mm from. maybe, is that the size of the fitting that is on the back of a saginaw pump? not the fitting on the pressure hose but the little adapter that screws into the back of the pump, then the pressure hose screws into it.
YES - you are correct on sizes, I was wrong
3. i have heard of people getting custom hoses made that will fit a saginaw pump on one end and the 4-bolt box on the other end. usually what they do is to take a hose that fits the saginaw and another hose that fits the box to a custom hydraulic hose maker. the hose maker uses half of one hose and half of the other hose to make it work.
9 had suggested doing just that, not sure if anyone has tried it yet or not.
THAT IS WHAT I WAS GOING TO TRY UNTIL I TOOK THE 97 F350 HOSE OFF AND FOUND THAT THE GEAR SIDE WAS INVERTED FLARE AND NOT LEAKING AND NO SLOP IN THE TUBE ATTACHMENT TO GEAR BOX.
SO I TRIED THE 88 BRONCO HOSE WITH THE 97 F250 GEAR BOX AND IT DOES NOT LEAK.
97 F250HD 4 Bolt - Master Pro 501-0118
88 Bronco Pressure Hose - Precision 13401261
I did not install the o-rings that come with the gear box in the gear box. Seems to be working fine with no leaks.
hope this answers your questions and again, let us know what you find.