I don't​ see any reason you couldn't achieve the same fit on both bikes. Ulitmately, all that matters is the position of the seat and handle bars to the bottom bracket. Differing frame sizes and angles can make this a challenge with readily available seatposts and stems, but your frames are close enough this shouldn't be a problem. Differing frame angles can make simple things like seatpost offsets and stem lengths misleading if the frame angles differ. Much better to level the bike, then measure seat and bar heights and offset relative to the bottom bracket with a tape measure and plumb line.
Getting them the same within +- 1/4" shouldn't be too hard.

I've got 57cm and 63cm frames that fit identically. The 57 has a goofy tall stem, and the 63 isn't showing much seatpost, but as far as my butt and hands can tell, they're the same. (That isn't to say they ride identically, they just fit the same.)