Got my 45 for Christmas and still waiting for buddy's help to install, run gas and elec, etc. Plan to mount in upper back corner of three car attached. Given the posts I've been reading, clearly want to mount at an angle in the corner to get best circulation/heat. Ceiling is 9' and sounds like bolting directly to studs is doable, but may create some fan hum in the bedroom above. Since ceiling is drywalled already, I plan to use to perforated angle steel (Home Depot/Menards/Lowes) to bridge between the studs at an angle. Probably need about a 4' length depending on the angle.
I'll lag bolt the two parallel angle pieces to the ceiling joists, then bolt a second set to those to form a [ shape, then bolt the heater brackets to the bottom of the L. Made this sort of bracket to mount my air and electric retractors as they wouldn't span the 24" joists either.
Finally, I plan to use some sort of rubber bushings when bolting the heater brackets to the support brackets in an attempt to minimize or (hopefully) eliminate any vibration hum. Had some luck with this concept for the door openers that still are pretty obnoxious, but expect the heater fan to be a bit less so.
Will plan to do some before/after photos once weather warms a little. It's been single digits in Chicago and we're destined for upper 30s this week. Ironic that you need the garage heated so you can install your heater!
Drums