I would suggest sticking to the modified ones. The new prototype chassis feature holes for front bulkheads in rear.. The difference however shouldn't be that big, just a little more flex..
Setup wise I'd recommend basically what Phil says as a starting point, apart from the 0 - 0.5mm shims underneath the front pivot blocks.. run 0.5-0.5, the anti dive only works on certain tracks.
I'd start with HPI silver/silver since this is 90% of the times the way to go, pink/silver is not always the best option out there.
I've included a basic setup that should work at nearly every track/surface.
Furthermore I'm happy to tell you guys that Kyosho is working hard on putting an 'upgrade' kit together. This kit will most likely include the new steel axles/outdrives, floating servo mount, solid piece suspension block(s), new topdeck and maybe a few other nice goodies. I can't tell you the exact specifications or release date yet since this is still unknown. Ofc I'll try my best to keep you all updated!
I've been driving around with all the new prototype bits for quite a while now and have to say that they work amazingly well! We made a lot of progress on carpet but on asphalt the car is outstanding!