KWA G36C Help

[Animalmother]

Well, i have a lonex POM pistom and a lonex red piston lying around.

My main goal was simply maintenance. I cleaned it out, used green slime and regreased everything cleaned contacts etc... You guys no the drill.

It's had no maintece since i bought.

I also have a systema m120s spring i am going to throw in there.

Hopup bucking sticks into the barrel it probably balloned from silcone oil way back when i though i was ok to lube it, i cleaned it up but its old.

M120s spring
Which hopup bucking? Systema work without compression issues? I also have a stock tokyo marui bucking.
I want to avoid surprises like compresssion issues. Yes the answer is stairing in front of my but i want to hear it from you guys.

Ill put in the new spring. The lonex piston head and piston though i am not sure if i should swap in. The stock one does had little bit of wear. I think the stock barrel is fine, dont see anything wrong with the inner barrel.

Which buckings work that have good?
I was thinking maybe the stock bucking and getting m-nub or namanzu. Whats the difference? Do i still need to sand down the bucking prongs if i use these?
Thanks guys.