currently have an 05 2500 hd with the nv4500 5spd. would the nv5600 6 spd. be any better for fuel economy and towing?? has 4.10 gears..... and would i have to change the clutch disc? i'm thinking it's not worth the hassle.

 

Would probably be, at least in theory, a tad bit better, but since you already have 4.10 gears especially, I wouldn't think its worth the hassle.