I've done this more than once.....
Love my 6.2's. My carb'd K-5 with a 350 got 13 mpg on a good day. The 6.2 powered K20 Suburban got 18 doing the same commute.
Now that K20 Suburban's motor is in the K-5, and it's got oversized tires. I use substantially less fuel than anybody I go wheeling with. And I'm on bigger tires than most of them.
05 2500HD CC LB LLY, 4x4, 3.73s 235/85R16's, webasto cab heater, to keep it warm.
03 Buick Rendezvous - When you average over 80 miles per day driving around, you need one of these.
85 K-5, 6.2, SM465, Rockwell T221, 1 tons, 36's. More goodies to be installed as time and money allows.
82 K20, 6.2, SM465, NP208, stock except for bed rack, snow plow, and glow plugs are on a toggle switch. It works great for plowing!
72 Postal Jeep - Yet another project