Longarms definitely along with a pistol
I'd go with:
-PJSS Model 55 Shotgun, it seems to basically be a double barreled shotgun. Not positive if there are rules for using both barrels at once, but you could probably come up with some decent ones. (AR78)
-Cavalier Deputy, 7 shooter, its SA so it doesn't totally gimp him out, and comes with no accessories so its basic out of the box (AE22)
-Or a basic Super Warhawk (SR4 317), like the Deputy, basic out of the box. six shooter but has more stopping power.
As far as armor goes, Leather Jacket
Custom Lifestyle:
Comforts: squatter
Entertainment; streets
Necessities: medium (maybe squatter but cowboys tend to have what they need)
Neighborhood: not sure
Security: street or squatter, maybe go higher if he's paranoid and does his own security.
Qualities (house)
-Stocked Up
-Rural Home
-No neighbors
-Hasty Exit
-Leaky Faucett
-Pest Magnet (1 or 2)
+/- 1400 a month
If he wants a vehicle, go Gaz Willie's Nomad, at least how I imagine that is that its an old run down pickup truck