Sturmey Archer AW3 is a fine choice.. get a wheel, built around one.
put it in your bike, figure out the gear ratio range you want,

select the tooth count of the 2, 1 cog and 1 chainring to suit.

High gear in the hub is the cruising gear,
the other are to go into the wind and over rises in the road.

Or if you leave the triple on the crank, get the 3/32 thick cog on the 3 speed
and use the old RD as a chain tensioner. then you have 6 speed, sort of.