Some input on the subject.............
When doing my conversion i encountered the same problem (3mm to much) when i used 90 discs, but in my case its more of a mish mash (series axle with discs, with 110 hubs). I used the 110 discs but i then needed to make spacers to line up the caliper bracket (like many others). To be honest its seems you will suffer the same faith, as putting 110 disks which are deeper on your hubs will make them hit the bracket.
As to calipers, i used 90/disco ones, with the 110 discs, its stops fine and they do work. But clearance between the disc and caliper is paper thin! It mainly due to the 110 discs being slightly thicker and larger in diameter.
G