The early model swingarms will work with the newer style carrier, but the alignment won't be correct because the holes that the carrier mount to are larger on the older swingers. This is because the older models had 4 large threaded holes to mount the carrier, and when you bolt on a newer model carrier the bolts have too much clearance and will not maintain correct alignment. If you make some bushings to reduce the size of the holes in the older swinger, then it will work just like the newer model swinger.
Sorry for the long post, just wanted to let you know what the difference is from someone that's been there/done that.