you have to be careful when buying the correct size taps, i haven't seen a set sold locally that has a 6-48 tap. it is a gun specific tap. i have a complete set of taps for 6-48 with the taper, plug, and bottom taps and also have the 8-40 taps. IF it was taped for 6-48 and stripped out then you would have to go up to 8-40. I had the same problem but the holes in my reciever went all the way through so i had no problem and the rifle runs fine. my set of taps came from brownells. a good bit of money but it is top quality and great stuff.
If your holes go all the way through then you can get by with just a taper or plug tap.
I've bought from this guy and the stuff is good:
http://cgi.ebay.com/8-40-GH2-4-FLUT...hash=item260347764323&_trksid=p3286.m20.l1116