'74 Compression Ratio

I have a 74 corvette with the base engine. I want to put a set of vortec heads with 64cc chambers but i am concerned about the compression ratio increase. I want to keep the compression ratio around 9.5. Would i have to change the pistons to do so? What is the stock compression ratio on a base 74 engine? How many CCs of dish or valve reliefs are in the stock pistons?

Any help is appreciated.

the stock compression on a base 74 is 8.5 - 1. I think putting on 64cc heads should b alright cuz i put on the edlebrock rpm performers and they were 64cc and the cars runs great.