I have an M14S/M305 with a TRW bolt, Fulton Armory barrel, springfield gas sytem and HR-N trigger group. If you use the TRW bolt on the Chicom barrel, you usually have to lap it in because it is tight. With the Fulton Armory barrel, the TRW bolt fit right in beautifully, about .002" slop. I had to put the springfield gas system on it because the Chicom one was a sloppy fit. I didn't have to shim it, it was tight. I also ended up with the right tension on the piston to op. rod. This centered very well too. The HR-N trigger group snapped right in. I reused the Chicom flashhider which fitted on well and tightened it down with a USGI castlenut which is a different thread than the Chicom. The front sight is straight thanks to Hungry showing me how to index the barrel. I have a USGI fiberglass stock that my receiver snapped into tightly. I put the Chicom buttstock back on it. I had to get a bolt from Home Depot to replace the woodscrew. I reused the handguard and filed the sides down so they don't touch the stock. I also have a leepers scope mount that I ovalled the side screw hole and shimmed the mount contact/stripper clip guide mount so the fitting and elevation is correct. Oh, if you get one of these mounts get proper replacement bolts. The ones they come with are real crap.
Mainly the M14S/M305 is metric threaded. Dimensionally they are very close to the imperial sizes so much that you can use virtually any USGI parts that don't have threads.
I think that is it. I hope I have answered some of your questions.
