I did the EGR conversion to my drum rear last summer. Also did front slotted rotors, braided lines on all fours and 5. 1 brake fluid. I'm fairly happy with the rear discs but I wish I had tried the bigger rear brake cylinder upgrade with the drums before I called EGR. I think I could've saved a lot of money and gotten close to the same results. As far as a whole different axle type conversion... I'm no help there. The EGR conversion isn't hard to do, just messy as all brake work is.
Good luck on your decision.
Chuck