Too high rpm - overdrive? Keisler?

I like the overdrive and additional gears on the GearVendor. I was working at a transmission shop and saw my first one there, and it was not working, causing a lot of 4WD problems on a truck. The truck was a true POS, and the guy had been driving it without reverse for two years, so I won't hold anything against GV on that account. However, I truly love driving a manual transmission. I don't know which way to go, but I am leaning toward a manual conversion.