Hmmm 4,500-6,000LB truck 4 wheel drum brakes ? not power assisted ?
If you can lock up all your tires like my 62' can i'd say fairly short . . . If you can't lock them up fairly long . . .
I can stop my truck and 22,000lb's of payload say 29-31K-LB's from 60mph-0mph in the length of a high way off ramp or less . . .
I never had a stopping issue honestly . . .
Mike