Iwama style has numerous jo kata, one of them may be the 31 jo kata you refer to, and there is a 13-jo kata as well which may be the "14" you're looking for.
If this sounds like what you're looking for, I highly recommend the "Bukiwaza" CD available from Yellow Springs Aikido in YS, Ohio. You can order them from the website here, but you can't do a credit card thing from the web so will have to call or mail a check:
The CD has video clips of the complete Iwama weapons curriculum as taught by Saito Shihan, including jo and bokken suburi, awase, jo kata (13 and 31), kumijo (31 and 1-10), kumitachi (1-6), and ken tai jo (1-7) plus variations, jo dori, tachi dori, tanken dori, etc, all done slowly so you can see what's happening, great for study.
Hope that helps.