VL36 (Abarth Grande Punto) and VL38 (Abarth 500) do differ slightly,
I believe the VL36 spools up faster but maxes out quicker (for more low end torque since the GP is heavier), whereas the VL38 spools slower but boosts higher later on in the rev range.
The manifold is the same for the VL37 (standard T-Jet turbo), VL36 and VL38. It would be perfectly fine to just swap the turbo and map it, but if you want more than around 155bhp you'll need to mod a few more things.
My car has: VL36
Turbo, Forge Intercooler, GSR Induction, 2.5" Catback exhaust, De-cat, Forge Actuator. Remapped and running 180bhp. Check my members motors thread (link in my sig) for more info