Looks like it's titled off the engine serial no. Your truck is actually a 6400 series 2 ton, or maybe a 6500 Heavy Duty 2 ton. A 4400 series 1 1/2 ton, would have push on front bearing dust caps, instead of bolt on caps. When bleeding brakes on big trucks always start at the wheel cyl. farthest away from the master cyl. first. Bleed the hydrovac booster first. Nice looking truck.
