R-414B is a coolant with claims of greater efficiency than R-12 and R134a. I used it in place of R-12 and it worked great. Unfortunately it leaked out after a few weeks. I since have corrected the leaks and recharged with (free from a friend) R-12. The cost for the R-414B was around $11.00 for a 10 ounce can. From what I read at
http://www.icorinternational.com/literature/PDF/HSFS.pdf#search='R414B' , it will work with no AC conversion necessary.