Welcome, Neighbors!
You may want to post your question in the section of the forum labelled "Fifth Wheels | Travel Trailers | Ultra Lites" under the "Rockwood" sub-forum. You will be more likely to encounter Geo Pro owners there.
I think you are on the right track by choosing an travel trailer (TT) first, then shopping for a tow vehicle (TV). The Geo Pro G19FD's gross vehicle weight rating is just shy of 4,000lbs. Use the GVWR to calculate all other weights and NOT the unladen vehicle weight (UVW). Figure your true hitch weight to be 12-13% of your GVWR, which is about 520lbs (not the 390lbs in the specs; that's based on UVW).
With those numbers in hand, you'll want to find a TV that has enough
payload to carry a weight distribution hitch (WDH, say 80lbs), the hitch weight of the TT (520lbs), the weight of all humans and other life forms traveling in the TV...plus the weight of all your cargo. Figure that's very roughly 1,300lbs (80 [weight of hitch] + 520 [TT hitch weight] + 300 [life forms] + 400 [cargo]).
So, when shopping for a TV, look on the drivers door jamb for this yellow sticker:
The number circled in
red is the payload of that specific vehicle. Give yourself some additional payload "room" by looking for your anticipated payload plus about 20% or so. In the example above, you'd be looking for a payload rating of 1,500 to 1,600lbs.
There are a lot of incredibly smart and experienced folks on these forums. What I have written are just the basic things to consider. Post over in the other forum and I'm sure you'll get good counsel!