Don't know what to tell ya.....
I have a 790 Bonnie with stock needles, and went to 42 pilots to ease some starting issues, and it worked out fine for me.
Just from doing some post comparisons, it looks like the 865's are jetting up pretty close to the 790's when still using the air box and either a single K&N or Uni.... but eeing as Dinqua has upgraded to a 904...I think he could answer you jetting calculator questions better than I can.
All I can tell you is it's "da bomb!" for 790's.