I was going through some of my old mags and found a 2002 GM brouchure on the Big Chevy Vans. According to that the 6.5 makes 195hp and 430 lbs ft of torque. What's the differences between that and the older 96-99?

Nothing as far as power #'s. My 98 was rated the same.
The van uses different heads and intake system with the turbo in the center.

Oh.. didn't know that.. my 96 is rated at 190/385. What did they do to the 98 over mine to get the extra power?

'98+ got oil spray piston cooling which alowed GM to up the power by way of computer programming. Except for the oil spray and the programing there is nothing mechanically different. To the best of my knowledge.