I doubt that there is one "best kit" in the market, but rather different kits that are "best" for meeting the needs of various buyers. If you ask me which is best, I'll tell you it's the one I have from MSA. If you ask Oiluj, he'll tell you the best is from Vintage Air. It's kind of a case of pay your money and make your choice based on factors that pertain to you and your Z. Are you able to do the fabrication work yourself? Will someone else be installing the kit? Is cost a factor? How important is it to use the sliders to control the AC? And more. All of the kits will make your Z cool and comfortable, especially if you have a set of rear window louvers. Only you can decide which is best, in part, by using the recommendations of others in this group. Based on my 41 years of owning an air conditioned 240Z, I can attest that the MSA kit provides ample cooling when the outside temperature is 118º where I live in the desert. Good luck on your search! Dennis