I've been hired to install a condensing unit in a 1940's or 50's ice cream parlor soda fountain. It came with a refrigeration unit, but its gone. Only the expansion valve and the tubing they used for the static evaporators is left. The expansion valve was probably original. It is for R-12, says it has a 45 orifice and is stamped K17R. There is roughly 6 or 7 cubic feet of refrigerated space and will be kept between 35 and 40 deg. F. I'm torn between a 1/4 HP and a 1/3 HP R-134A unit. Any advice is welcome. I was trained at Daytona Beach Community College in 95-96 and have been in business for myself since 2005. Thanks in advance, Dave