i'd start in the 300's, possibly 320, and work down, my guess is around a 300 + or - a size or so,
hows it running ????
you arent noticing a lean bog at wide open throttle ???
and yeah 3 sizes up for just kens porting may be right, but i'd say the pipe is gonna need a few sizes bigger too, although that pipe looks very stockish/DG looking, which doest flow much better than stock, i'd still try bigger and see what happens
and read and learn to do a plug chop, nobody, not even ken can tell you exactly what jet is gonna work for you, you have to fine tune it, with plug chops yourself,
and why is this the first time your asking us for jetting help on here ??????
/\/\ knowing how, and doing plug chops is the only answer to that question