I think the 3.73 :1 carrier has to be used with the taller ratios. The 1M-4205-B is the one used for the 3.73, 3.54, and 3.31:1 ratios. The Mercury cars with Merc-O-Matic are the most common axles with this carrier. If you dont have one you can buy a new one for the D44 with 19 spline axles from Randy's R&P. Here is a link.
https://www.ringpinion.com/b2c/Parts...RWD&DiffID=126