I really can't offer and advice on what size to go with, I have no clue what you plan on doing with the truck, or what your HP goals are...

155/50 is a very popular injector size though...

i would like 450 maybe 500 hp what do you think

A 155/50 would be a good upgrade, but you'll need to upgrade the turbo to match to get your power goals. You could probably bust 450 with 155's and a stock turbo though. 175/75's and a good turbo would also be a good combo to get the 500 consistently. Something like a MTW stage 3 with the 175's. The 155's and a hybrid or stage 2 would be good.

ford the 450 mark witch seems alot easy to get to what size nozzle on the 155s and do you think tunes tho mkm is good or who should i go throw thanks ??

155/50's or 155/75's. Talk to the tuner and see what they recommend. Who's injectors are you planning on using? Might not hurt to talk to them too.

I'd use Innovative Diesel or Matt at Gearhead for your tuning personally. There have been some negative reviews of MKM even tuning for stock trucks, doubt they do anything with bigger sticks. Just my opinion...

ok sounds good i will call Innovative about the tuning and im just rebuilding my injectors just cross the boarder...i live in Canada