Looking for more power
 

Already have a afe stage 2 intake with horn, big exhaust, 80hp injectors, #0 fuel plate, afc wfo, 4k gsk, mac plug, 60# valve springs, on a stock turbo in lift pump, what is the next step for power delivery valves or turbo first

Turbo, definitely. DVs without turbo are just going to melt things. Although to make a turbo worth doing, you may want to step up to 150hp injectors.

I am flowing a lot of fuel, no clue why i would need 150hp injectors. Delivery valves should make up for it... shouldn't it.

Only going for a killer b turbo 63mm

You won't need them, you'll just get more from a bigger turbo if you have them. You'd get more from it with DVs too, but more fuel without a bigger turbo is just going to spike the stock one way out of it's optimal range and make a ton of heat- unless you turn down the pump, which sort of defeats the purpose of adding the DVs or bigger sticks in the first place. You'll make more power with the big turbo at less boost than you will maxing out what the stock one can spin, and the stock one isn't making great use of the fuel you can flow already. Right now a better turbo is a good choice, more fuel mods not so much.

A bigger turbo would be the best choice of the two options you listed. What is your overall power goal?

Do you have a recommendation for a good single turbo set up for 500hp

A 63mm to 64mm turbo can get you there but I would go with a bigger turbine than the killer B has. The 68 turbine has treated me well so far.

I have studs and aftermarket head gasket, but should I do a super b special which is a 64mm, might still be having to tow and I know they say the 64mm is not a good turbo to tow with?

63/68 of your choosing would be a good choice