I want to put a trekking or compact triple crankset on my mid 80's Schwinn Letour. Someone has a Shimano M361 that is never been used but I'm not sure how old it is. Anyway it looks like the new ones are 9 speed and I'm wondering if a 6 or 7 speed chain will work with the crankset?

I have bar end pods that I want to use with a set of 6 speed index levers and that is the main reason I'm not upgrading the rear to more speeds.

Am I safe to take a wider chain with me and see if it binds between the chain rings and if not, it should work?
Thanks for any advice.