You'll be amazed how much water the stock 3155 pump can push, given larger hose diameters.
I ran mine through 1/2" hose with a temporary DT and although I never measured how much it flowed, it was WAY more than the expected 350ml or so per cycle. I can only think it was at least double, but again, I never measured it.
With that said, for a run such as your 50 feet, I'll bet you could run 1/2" hose on the outer diameter fitting of the pump and you'd still be fine.
Mine was less than 10 feet so I can't attest to the strength/head pressure over your required length.