Nitrous Kit Recommendations?

The only system I have used is Nitrous Express for EFI applications. Their solenoids and fogger nozzles seem to be very good quality. I've never run nitrous on a carb'd motor before, so I can't really make a recommendation.

What's the rest of your combination? You may need to make ignition and/or fuel system changes in order to use nitrous safely. Also the effectiveness of nitrous is dependent somewhat on cam design. If you have a lot of valve overlap, you will not get a full 125hp out of a 125 shot.