To get the engine to fit probably not very hard at all 250 parallel twin vs 450 single. To get the budget frame brakes and suspension to cope with the extra horses that will cost.
The kit looks like it got some very high end bits in it (wheels etc) you get what you pay for there is a 450 class run in the UK which produces some pretty good racing designed to replace the 250 proddy class as you can't buy a 250 proddy bike anymore (RGV250 NSR 250 RS250 etc etc) and stepping up to the GP class machines takes propper money ie not the chump change they want for this kit.
