front brake upgrade for 1997 k3500

[Gibson]

JF9 brakes were bigger-still, but VERY rare as they ONLY came on C3500HD trucks; and there weren't many of them built. And as the system wasn't "Delco", it was "Bendix", and involved 4-wheel discs, it'd be REALLY difficult and expensive to swap.

You're right, I've only seen TWO rigs with the JF9 brakes, both of them were Step-Vans, and one of them was owned by friend of mine.
I'd be a hard swap, the Step-Vans had Rockwell made square-tube axle housings, (like a scaled down unit from a Deuce and a half,) and Bendix brakes, totally different from a corporate 14 bolt FF axle, and with a much bigger pumpkin.
Can't remember the ratio, it was either 4.56 or 4.89.
IIRC, the GVW was ~12,000.

 

[454cid]

You can swap in gmt-800 brakes, but it's a lot more complicated than just the brake components.