Pinion Flange Kit install help

I picked up a factory sealed 3.73 rear differential. They come fitted for the manual transmission. In order to convert for the automatic, you need to remove the pinion flange and install a new one. See Pinion Flange Kit part# M-4851-M8A. Has anyone here made this conversion? I am in the process and have some questions. I got the old flange pulled. Installed the new seals. Getting the new flange on the splined shaft – requires a special service tool – that I don’t have. Short of driving it on with a hammer, what are you folks doing to install?

This website has detailed install info but I assume by now you found a solution: good luck !

Recommended
Special Service
Tool: 205-233 (T85T-4851-AH)
Installer, Drive Pinion Flange.
http://www.cjponyparts.com/skin/frontend/cj-pony/default/images/install-pdf/install_m4851m8a.pdf

I just used the old pinion nut to draw it down onto the splines. Then removed it and replaced it with a new nut. Not saying this is the best method but it worked for me without buying some specialty tool I would use once.