Lights still dim with upgraded electrical..

[helotaxi 5,000+ posts]

Well the big 3 and wiring was done professionally, so I know thats not the problem.

Having seen some less than "professional" work done by "professionals" I would verify the quality of the work personally before just accepting that it's good.

how long is your ground from ur amp to chassis?

That's pretty much irrelevant unless he's got a coil of 20' of wire laying next to his amp before it connects to the chassis.
What might make a difference is what exactly your batt ground for your big 3 is hooked to and then from there what your amp grounds are hooked to. The answer should be the frame of the truck for both. The answer should also be the same fram rail for both. The connection between the two sides of the frame leaves a lot to be desired from an electrical standpoint.