When I had my truck at 620rwhp it destroyed my 6l80, so I moved to a 6l90 and it was priced way better than circle d..any of those guys.
I found brand new 6l90 from used auto parts places (online you can find easy by searching a truck or van 6l90 (myc or myd - i forget) . It had no miles on it but they advertised it with 4 miles. When we got i shipped it was brand new ..never been used. was $1700 shipped with a 6 month warranty.

Needless to say we had a built driveshaft I sent back to adjust to new 6l90 size, we put our same stall converter in, same tune as the 6l80 had, and I drove it for like 20k miles on the 6l90 with no issues. Took it to track, thrashed it with no issues....just an idea for you..
Its not as good as a built 4l80 would be, but gas mileage is better and easier swap...
I figure it will hold up to 700rwhp no problems..

 

Keep in mind a built 6L80 will be way stronger then a 6L90. The 80 is a little stronger because the shafts are shorter which equates to less torque/tension on the shaft. It does have one less pack per gear, but you can modify/machine and make up for it.

 

did you tap on the turbo housing for boost controller?

 

Precision taps the turbo housing.

 

And I hate reading about someone making 50hp more with 3psi less boost lol

 

Lol truck is down right now guys having some issues on cold starts after the feed line was changed to -8 the fuel pressure sensor isn't seeing pressure since it's still on the stock line and is sending more fuel and flooding the engine and it won't start...gunna try tomorrow to unplug it and see if it just fails and starts

 

Took the truck out to the track today for they first time since the turbo install and it did pretty good. Ran 12.5 at 108. I was happy with it considering it's a crew cab and I had it loaded down with a jack and 2 17" rims and tires and myself (280)

 

Impressive results, Im glad you got to the track. Shows pretty consistent results compared to me. Im a little lighter, with less power. You ran 3 tenths faster and 4mph higher.

Congrats

 

thanks! I was pretty happy. I'm sure if i didn't have the jack and tires in the back i would have been able to drop at least another tenth. Track was sticky everything was dead hooking. Its so tempting to turn up the boost but dont wanna risk anything