This is the response I got from Tousley:
The M-5560-ZX3B is no longer available. A popular alternative has been the M-5560-ZXM1, which we have in stock. These provide a bit more drop and are a little stiffer than the ZX3B.
The M-18000-ZX3B runs $159.50, and in stock as well
So I guess my next question is would the M-5560-ZXM1 be liveable on a daily driver that sees mostly hwy miles?
ZXM1: 120-160 and 110-280
^^ Why are the rates different for the same spring?
Since this seems to be the best bang for your buck I will probably end up doing it but I just wanted to get some insight from the experts
If you can't wear it out, burn it off