4 Lug vs 5 Lug....What do you think?

I have the stock rearend and spindles and had planned on 4 lug.I now would like disc brakes on the rear.Is there a conversion for the rear to use discs and still use 4 lug? Is it not to expensive to just buy a 5 lug rear with discs and replace the front spindles as well?I know this might be expensive but the drum brakes on the rear bother me.Also the car is only at the brake and fuel line stage so everything is still easily accesible.Go ahead,let me have it! Chris.