Yeah what 95 said...
Greg Evans is the guy who makes them, the FTVB, and started out pushing them towards the Ford Lighting drivers... well you know us diesel guys... we hear about a performance part and jump all over it... The FTVB is a direct replacement of the stock valve body.. pull the old one off put the new one on... I still haven't tried the one I have... Just not enough time..
The other kits do what the FTVB does but there are supposed to be some secret kinda things in the FTVB that make it better.
The Transgo is a full shift kit... springs, the sonnax valve, valve body plate, even some stuff to do to the pump to make it better... if you want to pull the tranny. I myself, on my truck, opted to just do the valve body and plate. The plate has holes that you drill with different sized bits making it so you can custom tune how it shifts. larger holes = firmer shifts... to large of holes and it almost is obnoxious.
The sonnax, tri spring is the same as a Transgo but without the plate and pump stuff.
And as they were listed they also fall in price... the FTVB is around $200, the Transgo $100 and the Sonnax about $50