Don't know that much about the Gen 2 platforms but wondering if there is a difference in length or wheel base between  like a 2001 4 door Vitara and a 2001 Grand Vitara? See adds for grands and just Vitara and don't see much difference?

Dimensionally there is no significant difference between the two - the wheelbase will be identical, and if there is a difference in length, it will be cosmetic - as an example, the GV has plastic trim on the lower body which the Vitara lacks.

The "gen 2 platform" Vitara was only sold in the US & Canadian markets, the rest of the world had Grand Vitaras in two door (convertible) & three door (hard top) with 1.6 & 2.0 inline fours, and five door with 2.0 four & 2.5 V6 engines and the only visible external difference between a 2.0 five door GV and a 2.5 five door GV is the V6 badges.