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I will be adding a 24V slave to the cab. Pray tell, what threads are the 4 tapped holes that holds it? Are they 1/4-20 or 1/4-28. I need to chase the threads and don't want to screw up. Also I recall reading somewhere that the positive cable goes to the starter motor, where does the ground cable get attached? Thanks much from the old and slow.

The ORD 9 calls out 1/4-28. The ground connection will depend on weather you are using the correct stock receptacle with the correct stock cable lengths for the M37 or a generic M series replacement.

Correct original negative cable attaches to the left running board's front hanger bracket. If you have a longer generic negative cable go for a substantial main frame connection or if long enough even an engine block connection.

Do you not have a copy of TM 9-8030?

I was going to guess and say they are 1/4-28 seemes like the military had a thing for fine threads back in the 50's and 60's. Maybe they thought if it was fine thread it would take longer to fall out if it came loose?

The rather higher occurrence of fine threaded fasteners in MV's was really just a commonality of parts issue. The aviation sector used more fine thread fasteners and their added use in the MV's resulted in less burden on logistics troops. Also finer thread pitches do retain torque better than course threads and are less prone to heavy corrosion since they seal a bit better.

i just recently pulled my cover off and thought the bolts were smaller than 1/4".....I'm curious now

They are 1/4-28, I was going to replace the originals with new, but when I saw they were 1/4-28 and different lengths, It wasn't worth the trouble for four bolts.