A tach is a 'must' of you want to get the most out of the performance of the car. Not knowing what rpm you are shifting at is almost like not using headlights at night: you have an idea of where you are going, but you don't get there as efficiently. If you are relatively new to performance V8's or even to the particular cam grind in that car, then just shifting by the sound the motor makes without a tach is a mistake. See if you can get a tach hooked up, then go from there. The ideas about the cam grinds above are pretty good, especially regarding streetability. The last one mentioned (Summit K-1103 grind) is a '350 hp' cam.: the torque starts down low, which is great for the street, and the hp tops about 5500 to 6000 rpm if I remember correctly. You engine combo can handle a lot more cam, but if it is streetability you are looking for, that particular grind is a decent one for cheap that will do very well at the stop light grand prix. Now, there are other cam manufacturers, like Crane and Comp Cams, that make great cams--you can call their tech lines and discuss what you have and what you want it to do, and they can give you some great suggestions. Just food for thought.
Davy