I have these wheels on an old Schwinn, the rear is 120mm wide so it should fit in your old bike, they are great wheels, you can probably find just the rear wheel on eBay as well, which is all you really need and it will be a little cheaper but buying just the rear wheel isn't as good a value (although bikes with different wheels front and back are cool).

http://cgi.ebay.com/TRACK-FIXED-GEAR-SINGLE-SPEED-WHEELS-WHEELSET-27-RARE_W0QQitemZ380108535383QQcmdZViewItemQQptZCycling_Parts_Accessories?hash=item380108535383&_trksid =p3286.c0.m14&_trkparms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

Check the links posted above, you'll find everything you need

you will also need a fixed cog, lock ring, and a 3/32 pre stretched track chain , assuming that you can get a straight chainline with your existing crank and either your little or big chain ring, although you should read what Sheldon Brown has to say about crank arm length:

http://sheldonbrown.com/harris/cranks/130-single.html

(a lot of fixie riders use 1/8" chains, but you need have a cog and chainring for 1/8" chain if you want to go that route)
and you should prob. read this too:

http://sheldonbrown.com/deakins/how-...onversion.html

where do you live? is there a community bike garage in your city? just take your bike down there and they will tell you what you need to get and help you install it