I took one off a 39 STD and it fit my 39 DLX ok. What I can tell you is the 38 is different and 40 is different (as Kube noted). If you think about it the 38, 39, and 40 floors and firewalls are actually all different. I wound up taking two and making one. Unfortunately, with exception of the 40 unit, they all look alike on the computer and at the shows. Suggest measuring O/A length and spacing of attaching holes at firewall "lip"...