79 rear brake conversion

I have a 80 K5 blazer with 79 8 lug rear ends under it. The truck has been lifted and is riding on a 35in tire, so you now it doesn't stop the best in the world. So, I was thinking about upgrading the rear brakes to disc. I'm a poor boy just like the most of use, so i was wondering what would be the cheapest and best way to do the conversion.