Riley, replacement blower motors have three speeds, as opposed to the OEM two speed motors. Since our fan switches only have two speeds, you have to pick which two of the three speeds you want to use. Pantera Electronics has a console switch controller that allows you to use all three speeds, as well as a ton of other improvements and cool features. Have a look: https://www.pantera-electronics.com/csc.htm
Also, the Vendors have a heater/evaporator unit that has a bigger evaporator and a smaller heater core, in order to improve A/C performance. I bought one from Wilkinson years ago but I've seen them on eBay too.