I don't know what bus, but it was a somewhat new school bus, probably early 90's. Disk front and rear.
I have looked at some of the new big Chevy trucks, they have nice axles with disk front and rear. If you could get a good deal on a wrecked one that would probably work.
You may want to take a tape measure and start measuring trucks you see with the brakes you want, even at the dealers lot. Check for spring pin center to center measurements and track width.


1951 GMC 250 in the Project Journals
1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-