I have a 2019 3761fl here are my dimensions hope they are the same and this helps. Note the doors that open up the door does make the height smaller by about a half inch, but it looks like the strut can be removed.
Right side(door side)
front
29 1/2 H
16 3/4 w
Rear 1 (long one)
14 1/4 H
58 3/4 w
Rear 2
14 1/4 h
34 1/2 w
Tail
30 h
51 1/2 w
Left (sewer side)
Front
29 1/2 h
21 1/2 w
the rear on the left are the same as the rear on the right side.
These are pretty close but caution may be different because the year.
I bought these when i had my other trailer, they almost fit because of the door in the way, i had to take off the lids to get them in without stuffing them in there or removing the strut.
https://www.zoro.com/plano-molding-u...56/?q=G1803256