Is the 3pk and 3pks still good radios I know they don't sell them anymore but I was looking to buy one but want more information about it.

Sure they're good radios but now rather obsolete (I have one of each that just sit on the shelf).

Other than lower latency (if you're looking at one with a 2.4Ghz module,) there's really not much that newer radios do that they won't... either model will still have more features than most people/racers will ever use. Finding extra rx's for it would be a bit tougher since you're mostly limited to the used market, but if the price is right then either model is still quite capable. We owned two that we used for quite a few years without issue.

Receivers are still very plentiful new.