Re: Looking for information on an 84 K20.
Locking differential means a G80 RPO code in the glove box, it is the Eaton Gov-Locker. The general concensus around here is that it is a pile of crap.
The 4-speed is the SM 465.
It's a New Procees model 208 (aluminum case) or model 205 (cast iron case).
2) It's a corporate 10 bolt front axle. GM stopped using the Dana 44 around 1980, a few '81's had them from leftover stock. Look at the rear differential cover, the number of bolts holding the cover on is how you ID the axle, for the most part. If your gear ratio is 3.42s I think it's the 14 bolt semi floating rear axle, 9.5" ring gear. I think 3.73:1 is the lowest (numerically) you can put in a 14 bolt full floater.
4) A good rebuilt quadrajet is regarded as one of the best off road carbs.
5) No, it means that it used to have automatically locking ones on there and someone has removed those and put manually locking ones on there.
6) The SM 465 is regarded as being bullet proof in most respects. A built 454 won't make it wince, a 350 sure as heck isn't gonna bother it. The 205 transfer case IS bulletproof, just not a very good low range. The 208 transfer case has a better low range, but the aluminum case is weaker. 33s and 35s are not large tires (considering the largest DOT approved off-road tire is 49" tall), the 35s are about all you want to put on the stock 10bolt front though.
7) Frame cracking where the steering box bolts up to. The stock steering is no bueno for offroading, when you articulate you loose your ability to steer.
8) What kind of parts? There are still thousands of these trucks on the road (we own 4 alone), and parts are still very plentiful.