The T-150 and T-18 have different bolt patterns. You can use the same bellhousing, but need to use different holes for three of them, the top left hole, you will have to install a stud through the back of the bellhousing and "press" it in. You will see what I mean if you hold it up to the tranny. There is either a hole for the stud or a "knockout".
If the tranny is a T-18, the first gear ratio is not 6.32:1. That is for the T-18A. The T-18 is 3.72:1 (or something very close to that). Still a very good tranny, very strong, just not as low a first gear. Check the number, it could actually be a T-18A, and you might not know it. (Many of the Fords were T-18, though).
As far as the shaft lengths, etc., you'll have to check the Jeep Specs to see what you will need to do to match it to your setup.
Good Luck, you'll like it anyway!