I have done the top end of my engine. Dart iron eagle heads which increased the compression from 8.5:1 to nearly 10:1. Edlebrock performer intake. 650 Demon Carburator. Short pipe headers and dual exhaust. The car runs great and I am sure I have probably added about 100hp. Just wondering where to go next without tearing into the engine to do the cam. I only have 54,000 miles. I figured I'd wait to do the cam when the engine needs to be freshened up. Thoughts?

Curtis, What about your torque converter, rear end gearing, suspension components, brakes, ignition ststem, and steering?   

Assuming you have seen to the safety items mentioned above, the two areas where you will feel the most impact are the cam and torque converter.  I know you said you didn't want to do the cam, but you have a terrible cam from the factory.  It is not a big deal to change a cam in a C3 Vette.  And if you go to a higher stall torque converter, you will feel the difference off the line.  Rear gears are an area where you will feel improvement, but at a price of higher RPMs and poorer mileage, not to mention higher up front cost than either the cam or converter.

One old guy's opinion

Larry

From an engine perspective, the cam would be my next stop also.

How can I tell what gears I have in my rear? I turn about 2500 rpms at 55mph and about 3500 rpms at 80 mph. My car has a turbo 350 transmission. Does anyone know, can you do the cam with the engine in the car if you remove the radiator?

You count your rear end ratio by first safely supporting the back of the car with both wheels off the ground.  Then turn the wheels one turn and count the turns of the driveshaft.  To be more accurate, turn the wheels ten turns and divide the driveshaft turns by ten.  

Yes, you can change the cam in the car.

Larry

Yes you can replace the cam if you remove the radiator. It also makes good sense to do this now while the heads / valve springs / guides are new.

  My next Mod would be a 700R4 Trans. Although on the Drag Strip the TH350 is still the way to go with a Higher stall Converter and  Deeper Rearend Gears on the Street the 700R4 will do wonders.  It will be faster out of the Hole and get better Gas Milage on the Freeway. Add a Higher stall Converter when You do it for even More but the Converter and Cam should be done togeather.

Thanks for all the input. After the answer on the rear gear ration, I feel pretty stupid. Very simple. 2 more stupid questions. Is the 700R4 also an automatic and is it a bolt in replacement? I am assuming it's a 4 speed automatic. What other modifications are required such as the shifter? Tell me more about the converter. Again, I am assuming this is a fairly easy job once the transmission is out.