First, the "Standard" garage door opening is 7' not 8'
There are 8" rims and tires
that have been used on tent trailers out there that offer some degree of lowering, but having an A/C on top may well be the deal breaker.
About as low as you can get is with bare 8" rims rolling on strips of 1/4 plywood (to prevent floor damage) and I believe that gives about 6" of additional clearance.
Measure the current height of the center of the trailers hub, subtract about 4.5 " from that number and you will have the approximate amount of drop you will get with 8" rims.
But again, good luck in finding a garage with an 8' door. Converting a 7' opening to an 8' opening often requires major structural work and may not even be possible in many cases.
Covered storage and even indoor storage are common RV storage options in AZ.