am looking at a crankcase evac syst for my 292 has anyone built one before and had any luck with them?

Are you talking about the kind that has a siphon tube going from the filler cap on the valve cover to one of the collectors? That is a universal design that has been used for many decades. No luck is needed to use them. What issues are you thinking you'll have?

yes the siphon tube style. I was just wondering if anyone else had used one and if there may be something different that a 6 cyl my have related to a 8 cyl.
I would think if you are using a 6 -1 collector there may be even more siphon power as there is a lot of exhaust movement.

Not really, a V8 uses 2 siphon tubes, one on each bank, so it has more siphon potential than the 6 cylinder because of having 2 more cylinder pulling it out. It's probably overkill unless your making some big HP. A vacuum pump may be something to consider though.