Well, I live on the (mostly) flat-ish prairies, so steep hills would be uncommon (but not rare). Likely wouldn't load it up heavily or max often, if ever. Currently has 20x9 tires with a 1955-57 Chevy 235 and basic 4 speed.
Most likely, I just want to reduce RPMs on the highway, rather than increase speed(a few people expressed their concern about running those engines at high RPM). To do this, would the gear swap or adding another transmision - a brownie - be easier to perform and find parts for?
Seems the gear swap is easier, but only if I can find the needed gear.
The transmission would be easy to find*, but then there is the mounting, shaft attaching, shift stick modifying and shortening the drive shaft.
*I know of an old GM truck manual 3-speed(more like 2, as 1st is marked as Low).