pastorbobnlnh 

Justin, welcome to C&V. Believe it or not, 9 speed is not quite vintage, yet, but we are a friendly bunch, and we'd never make some snarky comment like, "Why don't you just mount the latest DuraAce Di group?"

In fact, most of us ride a wide range of different bikes so you did come to a place that is helpful. I'm running a Deore RD (don't remember which model but I believe it was for a 9 speed cassette) on an 8 speed HG/UG hybrid cassette and my largest sprocket is 34T with no issues. I am using friction bar-end shifters and not index ones.

Don't forget you will need a longer chain, so purchase a new one at the same time. The chain will need to be shortened to the correct length, which can be critical when riding a wide range cassette with a triple crankset. If you don't have a chain breaker tool, buy one as well. A SRAM or KMC 9 speed chain with the quick link would be my choice.

Let us know how you progress. Again, welcome to our friendly little spot on the internet.