According to Supersix Motorsports, your 96-97 heads have the improved cooling ports just like the SC heads. If you get the SC heads, you will need 8mm bolts for the intake:
From Tom Y:
I've always liked the 96-98 3.8 cylinder heads. They are heat treated, have a deck just like the SC heads, same intake and exhaust ports, same combustion chambers, but they have 2 main differences:
1. They use a very light weight 7mm valve train for which we have bigger valves, great beehive springs, retainers, etc for .580 lift with .060" clearance.
2. They use 2 less lower intake-to-cylinder head bolts, but this has not been a problem on 3.8's up into the 19 PSI range. The other SC lower intake-to-head bolt holes line up perfectly, just have to use a different thread pitch lower intake to head bolt available everywhere.