Older 45 - 47mm Schwalbe Marathons had an actual width of ~41 (39 height). Room to spare without fenders.
If fendered, 40mm Marathons (37 actual) are my width preference for Tektro long reach or Paul Racer centermount. Excellent tires.
Here's a pic of Tektro LR caliper clearance with the 35mm Schwalbe Allrounds I used for a time (actual width of 36mm) before moving to another brand. The Allrounds were supple and light (~425g) but a bit delicate for my purposes.
