You need to get with your builder. A 6bt, NV4500, big twin stick case, D60 and 14 bolt will nearly weight 3k let alone the chassis. Then you mention a dt360 which has alot of torque and is typically a low rpm engine which you will want more gears I'd imagine but I haven't ever done much with those engines.

I suggest the 6.5l for weight savings and built right it will scoot a small rig down the road, they are economical, and parts are readily available AND CHEAP. No they are not power monsters but that's not what you put on your goals.

Might need some more figures for what they are going to use for a chassis and what the drive line will be pieced together with.

 

Chassis is tube steel.

attached photos include my minor alterations to their design. its not exactly a small rig




with your weights, i amend my original statement; rig will weigh between 4.5 and 6k unloaded

 

Didn't know tube chassis was made for towing, I'm not an off roader or rock crawler though.

Those weights sound realistic, you have to remember the weight of that Chassis doesn't include Radiator, inner cooler, oil coolers, batteries, springs, etc... Then you throw in a 1500# engine/trans package, big divorced tcase, and big axles with all the rock guards and steering linkage.

That's alot different than taking a k5 blazer that already has 1/2 that stuff on it and modding from there.

Also alot of those buggies have an all aluminum LS engine in them which is alot lighter and takes fewer coolers and such.