having built quite a few of these up, I'll add my 2 cents here.
BBls: For the money, Green Mountain is the best back for your buck. If wanting a leightweight one (aluminum, carbon fiber), look at Whistle Pig for aluminum or Magnum Research or Volquartsen for CF. Avoid Butler Creek. Cheap yes, but you get exactly what you pay for. For a plinker I guess they'd do, but for a good target gun, there's much better.
Triggers: I've tried the various DIY kits and they never impressed. For a bit more money ($80 total) you can send it out to TT Shooter and have an awesome trigger returned to you. Redoes the workings to a better design. For really nice, go for a JERD or for the best - KIDD.
Stocks: Too many to choose from here. I prefer those from Boyd's and Revival. Boyd's ha a larger selection of styles and colors and are nicely priced when you get thier stock/bbl package. Although not shown o thier site, Boyd's is now producing Barracuda style stocks for thier dealers. Great off-hand design.
Bolt: CPC - period
There's also the bolt buffer which for these just find one from whatever compnay you're already ordering from, all pretty much the same. Same with any extended magazine release although I prefer the clean look of the Volquartsen one. For those that have that "tactical" addiction and ned the hi-cap magazines; at least if you gotta have 'em make it worth your while and get good ons. The "lips" models are cheap for the same reason as the bbls are - you get what you pay for. tactical Innovations has the good ones, All CNC aluminum with ss steal feed lips or polymer ones with the same ss feed leips. Cost a bit more than the other fodder but well worth it.
There...that's the basics in a nutshell. For a build, just start with a regualr model and go from there or buy an aftermarket receiver and start from scratch. otherwise, I was very pleased with the performance of my factory "T" model. Also, since it's not a match chamber, it's fine for Stingers - mine loves them hot litle rounds.
Geeze this made me remember, I got a couple 10/22's that need completing soon. Spring's a comin', gotta hurry.
Here's a couple of the one's I've finished and actually have pictures of:
The "Nascar" one really is in .17 caliber so with that caliber and those colors it just worked out to be too close to be the #17 car. They've since been removed.