Casey,
The steering system if all new/rebuild should be fine at high speeds, it's just above what I'm comfortable with, it's not a poor design.
I'm not aware of any direct bolt on front disc brake setup for the medium duty TF trucks. The only way I've heard of others doing this is to replace the axle hub to hub.
After you get the front disc brakes done, find a modern rear with the gears you want and disc brakes and swap it all out. Replacing the entire rear is not that big of a job...cut the U-bolts, cut the brake line and disconnect the U-joint and the rear is out. Then slide the replacement rear in, bolt it to the existing springs with NEW U-bolts, connect the brakes and modify the U-joint and driveshaft to fit.
Whats the gear ratio on the GMC 6500 rear?
What's wrong with the 6-lug Budd's? If you swap in new modern axles (with disc brakes) you will more than likely end up with a different lug patteren anyway.
No matter what SBC you have it will have more HP than the original 160 HP 283, so you should be fine.
Mike B
