5 to 6 speed kits

[WarWagon]

I am looking at the SunCoast GM Allison 5-6 Speed Conversion 2001-2005 Part #: A1-6VB-TCM $1,648.00.
I wonder is anyone has experience with doing a conversion like this?
What fuel economy increase have you seen?
Worth it?

Would bigger tires be a better choice?

 

[THEFERMANATOR]

It will not pay for itself unless you drive 150K miles a year, and even then I doubt it will be worth it. Most who install it only see .5-1.5MPG increase. Bigger tires will drop your economy as well unless you go taller and narrower like the 235/85/16's. And I just can't see sending any of my money to the company that makes this after the way they did me in the past. And I'm not talking about SUNCOAST as they don't build it all in house, most of it is done by a company in Indiana. Theres several other reasons I opted not to do this kit as well from my research, many of which comes down to how the operating system for it is built and locked up tighter than fort knox.