Help please!!

[Adam Mac]

OK so heres the deal. Im compulsive so along with that i buy then run into problems. Typical, right. So now i got this marineland model 4 sump. And am going threw the process of buying a return pump and a hang on overflow box. What exactly should i be in the range of as far as GPH for both overflow and water return rate. My tank is an 80 gallon. And this sump i believe holds roughly 35 gallons. So total gallons would be a 115. Anyone help a struggling newbie!?!?!