cooling system

Chad here's what Scotty (from Scottysplace) uses for cooling his bad *** 10 second stroked 340 (416ci) Duster
Griffin Aluminum radiator - 27-1/2 x 19 <--a bit bigger than yours though
1 Perma-Cool HP series electric fan - 16"
180 thermostat
He says it's normally NEVER over 180-185 even when cruising around town, and he lives in Texas just like you.
Like the others posted, I say put a thermostat back in, get the fan spacer and go from there.
If you really want a fan shroud I'd check griffin and some of the other aftermarket radiator companys, it may be cheaper.