thats one way (and the best answer imo), although with three balls he can hit a four and then the three with one short the next ball.
There's another way too
County championship he can get 12 wickets a match for 16 matches, so 192 wickets (except he'd be called up for England with these stats)
50 over competition he can play 11 games so bowl 660 balls maximum, therefore to get a strikerate of 43 he gets 15 wickets maximum
T20 he can play 17 games...
surely a bit easier (than bowling northants out) - 100 x 8 = 800, +7 = 807 :)
(do you have to use all the numbers? if so: (100x8)+(7x(2+2-3))
and back to the cricket