I have thought about this a lot over the years...
Square body Suburban MUST have barn doors
4BT Cummins with the VE injection pump (the rotary VE pumps tend to be tougher, but make less power) with +25 hp injectors
GM TH400 transmission
NP203 range box with an NP205 that has been twin sticked
1ton early GM axles with 3.73 gears ( king pin Dana 60 and the GM/ AAM 10.5" "14bolt" both with automatic style lockers)
cutting brakes on rear axle
rear axle disc brake conversion
35" A/T tires
rocker rails, front and rear bumpers that have wrap around segments to protect the body with hollow fully welded construction to be used as air tanks, brush guard on front
Warn 8274 winch on a multi mount plate and wired so it can be moved from front to rear, or removed and secured
2 simple light bars, one forward facing and one rearward facing
single cylinder Bendix air compressor with a manual over ride for the unloader valve
dual battery set up utilizing group 31 batteries
From there it would just be camp equipment.
For the why, I have always loved Suburbans with barn doors. Being a diesel mechanic by trade it makes sense to swap one in. I would want a 4BT as opposed to the 6BT to get slightly better mileage while maintaining lighter weight, easy serviceability and durability. I would want a mechanical 8 valve with the VE rotary pump for better durability and to open my fuel options up (the VE pumps will handle much dirtier fuel than the P7100s so running waste oil is easy peasy). I would want the old school 3 speed auto for simplicity. The 203 transfer case had a removable gear reduction box and it is commonly adapted to the front of the cast iron gear driven 205 transfer case to get an additional 3:1 gear reduction. So total low range reduction would be 6:1. The 205 would be twin sticked so I can select front or rear axle drive seperately, this is important for using cutting brakes (kick the rear axle out lock one rear tire, kick the front end in and the truck will pivot on one wheel). I would need the greater gear reduction to allow me to lug the 'burb around off road with a 150ish HP diesel.
I would want an 8274 winch because they are the only US made winch that Warn makes anymore and I have seen them work harder than some 12K rated winches, they are also very easily serviced and replacement parts can be had at Napa. Also the design is 70 years old now, its lasted that long for a reason.
For on board air I would run a small truck style air compressor. This would bolt directly onto the little Cummins and be gear driven. I would simply rig in a manual over ride on the compressor unloading valve so it wouldnt be compressing air until I flipped the switch. For air tanks I would use the hollow cavities in the body protection.