so if I swapped the entire frame to a 4x4, what else would I have to do?
Well, you're gonna need a transfer case. 800 bucks. GM uses cases that bolt to the transmission, not divorced units. And the output shaft of the 2wd tranny wont work. You'll have to tear down the transmission, rebuild and replace the output shaft. That's 1200 ish at a shop.
Then there's 2 new driveshafts, and the combo tranny to t-case adaptor/tranny mount. 600 bucks.
Cut a hole in the floor, install the shifter linkage, boot, lever and cover. (much easier than replacing the ENTIRE under dash harness to use an electric t-case) 300 bucks
If you're using a 4x4 frame, you'll need a new rear axle as the 2wd axle wont bolt to the leaf springs 700 bucks
Hopefully your frame comes with the front axle, control arms, steering linkage, brake rotors, calipers, wheel bearings, steering box, because the 2wd stuff wont swap over. 3000 bucks
And since the 4x4 uses 6 lug wheels, you'll need 4 new wheels and tires. 1000 dollars. Tires, because the 4x4 uses 16" wheels, not 15 like your 2wd.
So you're over 7 grand now just to convert, plus the cost of the frame plus labor at shop, probably 4 thousand dollars. About a weeks labor time 40 hours at 100 bucks an hour. 11 thousand dollars.
You ready to sell the 2wd and buy a 4x4 yet?