anyone know what size fittings are used on a holley blue fuel pump and regulator
 

for the stock fuel lines?

3/8 to 5/16 IIRC. be sure to turn it down (close the line) before turning it on as the holley blue's fuel pressure is very high.

so whats is the proper setting of the regulator 3psi on a stock carb?

max 4.5 psi. btw, holley regulator came with 2 styles. 0-4.5 psi OR 4.5-9.0 psi. If I were you, I'll add a return to that regulator to play it safe.