The Tram is ok and about the same quality as a Larsen, but I don't find a Larsen with an N connector and you want that for an 800 antenna. For permanent outdoor use I would lube the NMO antenna threads and contact with some silicone grease then degrease the mount, attach the antenna and a mask off the antenna and N connector threads then prime and paint the mount and radials. That will give it a few more years of life before it succumbs to corrosion.
Here is a slightly cheaper price on that mount.
NEW TRAM 1470 Land Mobile Base Ground Plane Kit NMO to N Connector SAME DAY SH | eBay