Just had some work done on my "98" Monarch (built 8/97 on a 4/95 Spartan Mountain Master chassis)

The front axle was rated 9,000 lbs by Barth, but it is actually an Eaton EFA-12F4 solid axle rated at 12,000 lbs.
Perhaps the tire or suspension limits lowered the rating...

15.0 x 4 inch brakes ABB1-551-C linings:
Shoes: WK1308E-23KSB
drums: 3158X
seals: 35066

Drag Link:
310-228 Tie rod end
310-229 Tie rod end
347-300 Crosstube
347-003 Tube clamp

Reyco air suspension
air bag (Goodyear) 1R11-201

Eaton rear axle, model 19050S rated 19,000 lbs
Barth rated at 17,00 lbs

16.5 x 7 inch drum brakes:

drums (TRP) DB1657B
shoes (TRP) RK4311EPR23
axle seal 393-0112
air bag (Firestone) W01-358-9213

The parking brake warning light switch is on the parking brake air valve, mounted in the instrument panel.

Hobbs #76577 4 psi NC

All are widely available.