What parts to use is kind of like asking about religion. Can't really go wrong on an MSH unless it is plastic. If this is for a .22 or a non-carry .45 I would consider trying a reduced power mainspring to see how you like that for trigger pull.
On other parts Ed Brown, SVI/Infinity, Smith and Alexander, Bar-sto, some Wilson, all good parts I've used, buy quality stuff and you'll be ok. On the trigger you can buy an SVI trigger and use interchangeable faces, but each face is about $20, neat profiles though. I like a short flat face usually. MSH shape is a big part of shooting, for tactical type run and gun stuff I like a checkered flat or wedge housing, but I'll be damned if I can shoot them well if Bullseye is the plan, have to have the traditional arched housing to keep it in my hand.
