The Clark boards are compatible with Tamiya, they give and take hits and hit every requirement laid down in official rules.
It is not the reciever that is important, it just passes a signal with some code in it. The electronic board that generates that code is what is important.
Now that being said the Heng Long recievers are at a disadvantage when it comes to tamiya apples because they don't have the 45 deg defence, meaning the tamiya apples at a distance of 10' or less can be hit at any angle, beyond 10' the apple needs to be hit at a 90 deg angle to register a hit.
Heng Long apples register a hit at any angle at any distance.
I can show you how to put the 45 deg defence on your heng long apples if desired but it will have a 45 deg defence all the time.
There is lots of things you can do but my recomendation is to stay with the Heng Long apple and if desired move to the Impact apple as it is less expensive but basicly the same quality as Tamiya.
I stock the plug in cabnles that go toi the board so all you need is the apple itself.
Here is the Impact one http://mitosal.com/73003.htm
I don't know much about the SLU apple so I won't comment on it. As an fyi, you can make anybodies apple work with the Clark board.