GVWR is not the curb weight, it is the maximum weight of the vehicle when fully loaded. Assuming CJ's were still considered 1/4 ton in '77, curb weight would be 3250 soft top without payload.
Early CJ5's are much lighter than late ones. My '55 weighs about 2200. I need to weigh it now that I restored it, but I think it should still be that way. The tranny and case in it weigh about 120, the axles weigh about 100 each, the body weighs about 250, and the engine weighs about 500.
I think all the extra weight in the later ones comes from the heavier engines and drivetrain. My '55 has a 3- speed T-90 and a Spicer 18 case, both of which are cast iron but pretty small. The rear axle is a Dana 44, and the front is a Dana 25. It has an 11 gallon gas tank under the seat. The '55 has a 4" shorter wheelbase than the '77 and has very light manual steering and non-power brakes. The Buick 225 is cast iron but very compact compared to a 258 or V-8. It is actually lighter than the original F4-124 that was in there (At least it is with the aluminum intake). All that extra cast iron adds up!
1955 Willys CJ5 Buick 225 V6 160HP 270ft-lbs, T90 trans, Warn OD, PTO winch, Spicer 18 T Case, RS9000's, Dana 25F/ 44R,
5.38:1 gears, 11" brakes, Bestop Supertop, Hurculiner