Sort of depends on what you now have, doesn't it? I'm guessing you have no valves now, maybe just screw on caps for Pex tubing? There are screw in valves in various thread sizes that could replace the caps. Or cut off the existing fitting and use any brand of push-to-fit fitting (Sharkbite is just one brand), or a compression type fitting. They all work, and work well.
The main consideration is the degree of exposure to external damage. LP drains are often below the belly pan and exposed to road damage, so you want a sturdy fitting and one that doesb't protrude too far.