You want to keep your compression around 8:1 with a supercharger. 9.5 is too high for a Roots-style blower. With 8:1 you should be able to run 8-9 lbs. of boost but I would make sure to use a boost retard ignition box. A number of companies offer forged blower/turbo pistons for such a build. A 144 worked fine on the 350 I had some years ago, but I would opt for a 177 for a 383.