I'm not familiar with the 58, but on the AD trucks this is a bolt in swap, the front springs are same width for 1/2 and 3/4 ton, so axle bolts in the same.

I wouldn't downgrade a 3/4 ton though. Lots of 8 lug tubeless wheels are available. There are also a couple disc brake kits available for 3/4 and 1 tons the last couple years, if disc brakes were the main goal.

I wonder if the aftermarket 1/2 ton disc brakes are even as good as the3/4 ton drums? Brakes come in different sizes, so just being disc brakes doesn't make them more effective, depending on the compression.

Grigg

•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-