try with 16/52 and 21/47.

if this gearing cant reach top by end of the straight, then u might wanna try 15/50 and 20/45 or 16/51 and 21/46 if yr engine max-out too early on the straight.

about gears split, better to maintain same split for proper gear meshing...but still alrite to have 1 tooth different. no worries.