I will agree with what Pat said 100%.
I would look at a SRP piston part #142980.
This is a shelf piston.
This piston will give you about 9 to 1 with your heads.
The piston is for a 6.385 rod.
The longest rod I would ever run in a street car with a 9.80 deck would be the 6.385.
If it where a 9.80 deck in a drag car well then I might look at the 6.535 rod.