Ok so that 90 k5 has 10 bolts front and rear, they are not desirable. I wouldn't even consider using the rear 10 bolt, but if you have a semi float 14 bolt from the heavy half tons, it's a reasonable combo. That's what I ran in my k5 for a few years. Granted I ended up with chromoly shafts in the front. If you were to us that front 10 bolt, you'd need a passenger side flat top knuckle, drilled and tapped, and a high steer arm. Would also need an Astro van steering box. For steering, you could get by with simple crossover (draglink from pitman arm to passenger side) or you could get a drivers side high steer arm also and move the tierod up for full high steer.
As for leaves, are you talking about usin those in the front or rear? In front, they really are just too long. Not that it can't work, but they don't package well. Several people use Dakota rear leaves in front, or go with waggy front leaves. If you are talking about in the back, yea they should fit pretty easy, a few people have used those. I have lift waggy leaves, with a slightly longer custom main leaf in front spring under, with stock s10 springs spring over in the rear.
To make that tcase work in there, I believe you'll need a different adapter. Approachmedium actually sent me one maybe a year ago (thanks buddy!
) I can get the part number if you need it. However, I've never messed with that trans so I may be wrong, but for an auto, you need it. Also the input is the old style, so ~94ish and before would be the years you'd need for the input swap.
Now, let's say I'm in your boat and going 5.7/manual/ and axle swap.... Depending on skills, available parts, money, time, ect.... (Don't forget time and money).... I think I'd hunt down a 70s ford high pinion 44 with the weld on wedges and a 6 lug semi float 14 bolt, swap the 44 to 6 lug, disk brake swap the sf14b, crossover steering, stock waggy springs sprig over in front, and use your choice of driver drop case. 6 lug wheels are very common, the hp44 can get d50 gears swapped in, the sf14b has huge shafts, the driver drop axle makes packaging pretty easy, full width so it'll feel stable in the twisty stuff, and if you don't like 6 lug, you could always swap the front to 8 lug and put in the full float 14 bolt (Dana 44s can be easily changed to 5, 6, or 8 lug with a few parts swapped here and there)
Now about that k5 transfer case.... Don't sell it super cheap (unless to me
) becuase that's a fairly rare version and is exactly what you'd need to make the s10 computer happy if you wanted passenger side drop. Personally though I probably wouldn't go passenger side drop unless you had a Chevy or dodge old school Dana 60. In that case, axle swap it and never look back!
There's only about 19 million different ways you could do an axle swap, it just comes down to budget, time, parts, ability to research what'll work and what won't work. It's not cheap (it can be though) and its not quick, but the result makes for a pretty decent platform for offroad sheenagins that doesn't say jeep on it. It does still have it limitations thiugh.