honestly the nicer trilogies are pretty solid, i have a tactical which is pretty much the same as the pro. it already came with a delrin bolt, only thing i really think it needs is an externally adjustable reg and a nice asa.
stock lpr works fine, all i did to my trilly was turn it down just a hair and it shoots great. its internally adjustable which is kind of a pain...but once you get it set right it will never come out of adjustment that way either.
you can also buy one of these which will let you put any lpr on it if you dont feel like spending almost $50 for a palmers....palmers does make great stuff though.