HP to the ground?

I would not ditch the C5. It is a evolution of the c4. They have better oiling and 5 clutches are not uncommon. It is likely if you have a C5 that it already has a c4 bellhousing and converter. C5 TC and BH are about 1" longer and makes fitting into a classic tough. If that is the case, you only need a C4 valvebody to make it an improved C4. A change in gear will give you better acceleration, but highway cruising will suffer. I have 3.08 gears and 3000RPM's is the norm on the interstate. Tire size play into it as well. Has your carburator been tuned? What is the elevation where you live? Is the shortblock a stock 65? If so the compression ratio will be on the low side too.

You need those gears bad! I am sure the motor is healthy but the 3.55's is a good all around gear. I have that gear in my car and it is fine although I do not do a lot of highway driving.

4.11's are fun...If you have overdrive!