Well the nc23 is 25 years old now so finding one with a usable shock can be forgotten. ISTR your can use an f4 shock? The forks/brakes can probably be upgraded to carby Fireblade gear very easily to help with the heavier engine and give some adjustability if nothing else.
If I were doing this I'd use: 96-7 blade fork with 929/954 brakes, nc29 6 spoke wheels and discs so you have a 17" rear and front. Those wheels fit that combination fine, you need to do some machining on the rear caliper carrier area is all. Does leave you on a 160 rear though, is it enough for a blade lump? You won't get more in the arm so it'll have to be.
I am certain it's been done, have a look on 400greybike if you haven't already. The 600FL conversion is way easier though and would still give you a decent and reliable @80hp instead of the 400's @55hp. Anyone tells you a nc23 had 63hp stock, ask them for a dyno printout
