I'm not a match shooter, but I had a USMC Match rifle, and I can tell you what had been done to it.
rear lug welded on, bedded stock, bedded handgaurd to eliminate movement, unitized gas system, bedded buttplate, trigger job, medium weight Barnett barrel, McMillan M1ANM stock, screwed on front swivel, bedded stock ferrule, hooded match rear sight. (the GI match rear sight doesn't give you 1/2moa adjustment- that's what the hood does.) Mine had a standard front sight, and after talking to numerous USMC rifle team shooters, it was a matter of preference.
When I sold mine
, the gentleman that bought it (a prior USMC team shooter that shot during the timeframe the rifle had been built) sent me target pics of .9" 200 yard groups he'd shot with irons, so apparently, the work was worth the effort.