I'd contact Warren and get 155/stock injectors with a stage 1 turbo. Should give you 500 hp but probably 400-425hp with a tow tune. I wouldn't go above 175/30's without doing some serious turbo upgrades since you tow heavy. Even 175/30's need fuel pulled from the tune if you tow heavy.
I have not seen any dynos or met anyone that even got close to 500hp with 155/stock and a stage 1 (unless they also had ported intake, ficm tune, and maybe water meth)... maybe 155/30 and a stage 2 or 175/stock and a stage 2. There have been a couple of crazy dyno numbers but most common would be
155/stock and stage 1 = 450hp
175/stock and stage 1 = 485hp
155/30 and stage 1 = 470hp
155/30 and stage 2 = 485hp
These are more common numbers, not the far few and in between live tuning and lucky numbers.
Too many people jump on here thinking with just 155s and a stage 1 = 500hp
then when they get their truck dyno'd they think something is wrong or they don't want to post the numbers
Oh and this is not a dig on rollinearly99- it just seems that too many people get the same info regurgitated here on the forum. I am hoping to post this in hopes that someone does not google 500hp 6.0 and find this post and spread the word like gospel
I agree with the 155/stock and a stage 1, it is a great setup. but not a 500hp setup