89 F250 front axle & hub lockouts

[windmonkey]

Hello. I would appreciate any help with two related issues:

1. Can anyone tell me how to identify what model front axle I have in my 1989 Ford F250 (with 7.3 L diesel)? I am thinking it's probably Dana 50, but some sources I have seen say it could be the Dana 44 HD.

I can't see any tag on the axle, but there is a number cast into the diff housing: RD 820598. I went to Dana site and this number with the "RD" does not register; wthout the letter prefix it comes up as a 0.15" shim.

The axle shaft has 30 splines, & axle OD looks to be about 1.265". I am measuring at tip of axle with hub lockout mechanism in place, so it's hard to mike it precisely.

The doorpost tag lists axle code as 35, but I guess that refers to the rear axle. Same tag lists front GAWR as 4410 lb.

2. The reaon I am trying to ID the axle is to look for a part for the manual hub lockout which broke. The lockout cap says "MM" which my parts store guy said was Mile Marker. Inside the cap is a three-pronged hardened thrust washer thingie. This washer turns with the manual lockout knob, so when engaged the three prongs push on three peaks on the cylindrical part that slides to engage or disengage the axle.

Anyway two of the prongs on the thrust washer broke off. It sure looks like I should be able to remove one snap ring, replace this pronged thingie, and be back in business. But all the parts stores I call say I have to buy a whole hub assembly! In fact they are usually sold in pairs. Part of the general consiracy of planned obsolescence.

If anyone knows where to buy constituent parts for Mile Marker hub mechanism, let me know. Thanks.