If you're just daily driving the car, stick with the 5W-20. If you're going to be out racing the car at the drag strip, autocross, or hpde type events, bump it up to 5W-30, it'll keep the oil from thinning out too much from the excess heat.
FRPP HotRods Cams / American Racing Headers Long Tubes with catted X / Stang-Hi dyno tune
Saleen wheels / Steeda CAI / Corsa Xtremes, K Springs, Koni STR.Ts, UMI lca relo. Brackets/r lwr ctrl arms UMI adj. panhard bar / Camber plates / SR Strut Tower Brace.