I did a very cheap conversion on my MJ, I bought a reman compressor from ebay without any lube, I replaced all o-rings with PAG compatible ones, thoroughly flushed the system. I then put in the required amount of PAG, R134 refrigerant charge minus 15% of the amount recommended for the original type. The system works surprisingly well and blows ice cold air out the vents, this is much improved with the (Volvo) electric cooling fan swap I performed on it.