[Mach 1]

You need the kit just for the adapters that come with it. They allow the r-134 can to fit on your r-12 fittings. The cans use different servicing hoses and style connectors.

You dont need the oil additive, and I would even say dont use it, as this tends to clog up the screen in one of the lines (cant remember off the top of my head, but its the line going from the condenser to the reciever/drier I think. it has a screen in it, and likes to clog up when shooting that oil shot in there, so I say skip the oil charge. (seen it clog up in 3 out of the 4 conversions I did)

All you really need is the adapter fittings, servicing hose, and the cans of 134. 2 cans is normally enough, but you might need three.

If the screen clogs up in the line, your a/c will not blow cold at all, and then you have to change the line also.

Getting it vacuumed down is also a good idea for optimal performance, but not required.