Sprocket because you'll want the power running 36 on a 660. You need the high output oiler or some other way to get more oil on the bar. .063 gauge is best to allow for max oil flow. I just ran some 404 in the mill for the first time today, and I'm a convert - at least for the 30" bar I was running it on. I got 4 cuts on 1 tank instead of the usual 3 I get with my 3/8 chains - I think simply because they were cutting faster. Lasted longer too - I was in the middle of the 6th cut before I felt performance loss; my 3/8 usually start dropping off around the 4th 8' cut.