If his transmission builder put together his 4L60E in keeping what
@Aidan Kesler stated in his first post
and the OP doesn't beat on it constantly, it should be fine with the stated HP and TQ levels. 4L65Es come from the factory built to handle between 375-450HP or so...Also, I've built more 700R4s and 4L60Es for 400-500HP DD/Cruiser/fun vehicles than I can count and haven't had one come back yet because the owner overpowered it with either the engine or his driving habits.
As much as I like the 4L80E swaps, doing that in his particular case makes no sense given he just had his trans rebuilt with the caveat the builder put it together per the intended application.
OP should be calling his builder to confirm that his trans was put together roughly similar to what I laid out above.