I've tried vent mounts in various vehicles. I would rank them somewhere near the bottom of the list of potential solutions. They never seem to work out as well as one hopes.
I have a Kenwood TM-281A 2 meter ham radio and Uniden CB mounted to an Arizona Rocky Road overhead mount. I recommend it.
I am currently collecting parts and materials as best I can during the Covid-19 shutdown to fabricate a Garmin navigator mount for the top of the dash. It is basically a small 18 ga. plate with a bend for attachment points that use the same fasteners as the center dash bezel. You could use something like this to mount a head unit. See this thread for an idea of what I'm referring to - my mount will be shaped differently but the concept this the same:
https://wranglertjforum.com/threads/no-drill-no-cut-ram-cell-phone-mount-bracket.26473/
Panavise makes an AMPS pattern mount that would place your head unit to the right of your AM/FM radio. I intend to use one of these to mount my Garmin inReach Explorer+. For your '01 with manual transmission you would want P/N 75122-301.
https://www.panavise.com/pdf_indash/75122-301.pdf
Ironically, I have a P/N 75122-301 bracket new in a box waiting to be returned to Panavise. It was mis-packaged in a box labeled for the 03-06 with auto trans, which is what I needed. It is a well made bracket and should be a simple install when Panavise is able to ship the correct part sometime in the next two weeks (their workers are subject to the shut down as well, only a skeleton crew is working). If you want the part that I am waiting to return let me know and we can work something out.