Besides hp, wheels size, paint what else does a grand sport have different that a standard 96 LT1?

The horsepower changed is obtained by the LT4 components which start with the LT1 block and use the revised LT4 heads, cam, and intake. On the body there are small fender lips on the rear fenders to accomodate the wider rear tires being that it didn't use the wider rear quarter panels and fascia from the ZR1.

Here's some valid information from the top source!

http://www.grandsportregistry.com/96_specs.htm

Did you know that in 1996 you could get a non-GS Corvette (one that was not
blue with the white stripes and black wheels) with the LT-4 and 6 speed? It is
true, the only engine and trans that a GS Vette came with was the LT-4 and 6 speed
manual, but if you ordered a 6 speed in a regular Corvette in 1996, you got the LT-4
engine. And if you ordered the automatic, you could only get the LT-1.