I'm building up a multipurpose commuter/tourer/century bike from a mid-90's Fuji touring frame. This bike will see a lot of hard miles in NYC but few dirt roads. I am using Shimano Deore XT FD/RD, a Sugino XD600 crank/chainring combo, and in all likelihood a 7 spd freewheel (like the IRD), since the Phil Wood touring freewheel hubs are about a third of the price of a cassette hub and I want the best, most bombproof hubs for loaded touring.
This bike will be friction shifting for ease of maintenance in remote areas. Either downtube or bar-end.
I have had great success with SRAM chains, and would like to stick with them. My question is whether I could (or should) use an 8 spd chain such as the PC-68 with the 9 spd RD. I am somewhat new to modern systems. I like the idea of having a stronger chain for touring and have heard that 9 spd chains are more prone to problems than 6/7/8 spd chains.