I just posted a thread about this the other day.... I have been looking at an Ultima builders kit for my bike ans was wondering if it's worth it. I can get the kit online for $499. I think this will be one of my winter mods
I did the Baker conversion with my 5 speed box. 6 speeds are a lot better, but Baker will cost you a lot more than the Ultima. To me it was worth doing because I was building a new engine at the same time.
I have the Rev-Tech drop in in mine. It has about 7000 miles and no problems behind a 127" Ultima. 6th gear is a bit high, unusable below 75MPH (2500 rpm) with the cams in the engine. It sure makes 85MPH on the interstates effortless.