with my 4.56 adn 285/70R17 (32.5") I shift into 3rd at 75 lol.

 

More HP will get you there faster. Top end speed is all RPM and gearing. Unless your engine makes more higher rpm HP and survives your top end speed will suffer. Tranny gears will give you the best of both worlds.

 

I can still pull clean to 140 mph, with some left on a 29'' tire..

 

Yeah! procharged 6.0 no problem lol

 

Seems to me that with my setup and 4.10s id lose about 10ish mph off of 2nd. So if I leave 2nd at 96mph with 3.42s then id leave 2nd at 86mph with 4.10s. Saying I keep the same rpm shift point ect..

 

Na man thats just the site name. It is just a bolt on 4.8 I still think 410's will wake your truck up..

 

Ohh sorry must have confused you with someone else!!

I may get some and try them out. If I dont like them I will just stick the 3.42s back in.... How hard are they to install?

 

http://www.f-body.org/gears/
Here is a pretty cool calculator. For a 4L60E the gears are
1-3.06
2-1.625
3-1.00
4-.070
Just plug in your tire size, gear ratio, and shift points and it will give you the mph

 

With 4.10s id lose 8mph in first and 16mph in second. So id shift out of 2nd at 82mph @ 5800rpm.

 

looks like its time for a cam lol