I would be comfortable with a 2:20 transfer arriving with hand luggage only, as checked baggage delivery at KUL is notoriously slow. Inbound C/F passengers get a pass for a priority immigration lane, but immigration at KUL is usually quite prompt anyway.

I've taken that bus half a dozen times, and the word 'enjoyable' doesn't come to mind . Unless it is one of the newer A/C'ed busses, the old ones are certainly a disgrace to Malaysia, and would have been at home in a third world country 40 years ago; if one of those show up, make sure you hold on tight to your luggage and don't place it near the (usually open) door. In my mind they (and their paying nature) can only have been MH's vengeance for yielding domestic routes to AK...

The bus departs from the normal long-distance bus terminal (not particularly well marked) accessible by covered walkway from one of the bottom levels of the main terminal at KUL. Pay the (~RM1.50?) fare directly to the driver.