7.5-8:11 CR would be a good compression to shoot for if your using a blower.
Forged pistons are a very good idea. You'll also want to get a cam designed for use with a blower, as they generaly have a wider LSA.
You ought to do some research on the torque capacity of the Jag rear end you have. I can't say from experiance, but from what I've read and heard, putting one behind a blown motor may not be a good idea. Jag engines are not really known for producing high torque.