I thought I knew that AX15s had poor ratio choices, so do some research. They are not a particularly strong gearbox. I'd go Mopar A833 OD before I did that
The ratios are: 3.83, 2.33, 1.44, 1.00, 0.79.
It's geared low in first to be used as a truck transmission. I've heard different things about it's ability to handle abuse in different applications. It seems to hold up pretty good in Dakota's and Jeeps, but not so well as the AR 5 GM variant in Colorados that have been LS swapped making over 300 HP. The Toyota R154 seems to hold up to turbo 2JZ's.