What budget torque converter?

I would determine most common fwy rpm, and try for a converter about 200 rpm less. It will not be slipping at freeway rpm.
It will go much quicker with a tc stall at peak torque... but you would probably have to change rear gear.
Compromise is somewhere in between.
I would expect to pay at least $600 for a good converter today.
Check out Hughes converter videos on you tube. #5 on stall speed is particularly good/informative.