The 98-02 F-body and 98-03 Blazer rear disc brakes are cheap if you can find an axle on Craigslist or at the boneyard to rob of the backing plates, calipers, etc. They both require you to make a no-turning-back change to your 7.5" 10-bolt. For some reason (likely savings in labor) GM changes from a four-bolt trapezoidal bolt pattern on the axle ends, for the brake backing plates, to an elongated 'tab' with a two-bolt pattern for the backing plate and a large hole for the wheel cylinder, with a clip to retain it. This made them easy to assembly at the factory, but allowed the wheel cylinder to float a little and permit some slop in the rear brakes. The mod to the axle is to cut off the tab and drill four holes. What I discovered when I did this, using the F-body backing plates, is that I ended up with the old GM trapezoid pattern. Two of these holes, ironically, line up with eh G-body holes, just need to bore them out. The other two you have to mark them and drill them out yourself. Use care to get them right, and there is not a lot of meat left on the tab.
What I don't know for sure, but others can confirm, is that aftermarket disc brake swap kits for legacy cars like 64-72 A-bodies and 70-81 Camaros are probably bolt-on once you cut and drill your axle to the trapezoidal pattern. One of the main advantages, besides cost, is that both the F-body and S-10 rear brakes use a small brake shoe inside the 'hat' of the disc brake rotor. GM used calipers through the 70s into the mid-80s where the caliper had an arm built into it that acted on the back of the caliper cup. The 89-97 F-body 'PBR' calipers had a slightly different take on the cam/lever arrangement (others weigh in). If either approach hung up, you had problems driving down the road. The aftermarket kits I have seen have varied choices for calipers and parking brakes, but expect to pay $450-$600.
Here is a step-by-step F-body conversion:
https://gbodyforum.com/threads/how-to-camaro-rear-disc-brake-swap-to-g-body-axle.55480/