On all the S13 and S14 5-speed SR20DET clips I've ever seen, the axle code listed on the firewall tag was "RC40" indicating a ~4.0:1 R200.
Nissan axle codes:
R = RWD
A = R160, B = R180, C = R200, D = R230
## = ratio rounded to the nearest tenth
If you're pulling a diff from a J30 and you're unsure of the ratio, RC39 will be the 3.916:1 box, RC40 will be the 4.083:1 box.
Automatic S13/S14 SR20DETs had the 3.916 ratio.
The 3.692:1 ratio was included with the six speed in the S15.
Here's some proof:
I could find more... anyway, find a shot of an S13 or S14 firewall tag indicating an SR20DET, a manual transmission (FS5W71C), and an axle other than 'RC40', and I'll believe it.
- Ryan, FIREWALL TAG NAZI!
Edit: just an aside... the CA18DET ratio was indeed 4.363:1, manual or automatic. Their tags say 'RC43'.