Better parts for performance applications. Usually have higher compression pistons, lower friction narrow moly or chrome rings, better than standard bearings, depending on the kit it can have lower weight pistons or gudgeon pins. Pistons are usually higher in silicon for less expansion than standard pistons which allows tighter piston to bore clearance, the race series head gaskets are tougher.
Not nesseserily, there is alot more that will effect that too.
Depending on how much you plan to rev it but you would want the conrods to be able to handle it, and have the whole bottom end nice and balanced. Also have the correct valve springs to handle high revs without bouncing.
I have a red 308 with acl kit and standard rods, it handles 6500rpm just fine. If you want to rev more than that then you might need better rods although if you have a vn or onwards engine then it has better rods already.
