As rhmc24 has pointed out, there is a big difference in prices for original '60 Armies and the modern repros, in addition to gunsmithing costs. I personally would not shoot
an original '60 converted to .45 Colt. Assuming your friend is willing to go the modern repro route, then he has some options. Uberti in Italy makes all of them, the only differences being the importers specs. I have two Cimmarron 1872 Open Tops in .44 Colt and two Cimmaron 1861 Navies (percussion) in the charcoal blue finish,and they are excellent. I don't have hands on experience with any of the other importers offerings, so I can't speak to them.
I earlier linked to the Open Top and Conversions sections of Cimarron's website; here is a link to their percussion revolvers:
Percussion Revolvers
Note the conversion cylinders at the bottom of the page. There are two types; one for an unaltered percussion gun, and the second "gated cylinder" type, meant for a revolver that has had the recoli shield reamed out so that a cartidge can be loaded from the breech, like the SAA and the conversions. However, as I understand it, doing so makes the gun a "firearm" under Federal Law, although one can load and unload fast. The first type requires removal of the barrel for both operations. Also note both types of .45 cylinders hold only 5 shots. If your friend requires the "look" of the graceful unaltered 1860 Army, with the relative ease of breech loading,that's about the only option.
If he wants the same option, but will go the 1851 Navy's looks and caliber, he might look into this:
Man With No Name Conversion .38 Colt & S&W Special, 7 1/2 in. Barrel
This is in .38 Special, which will be easier on the wallet. Speaking of ammo, all of these guns are intended to used with "cowboy" loads, not the hot Plus P stuff.
One other thing, even though you can order the percussion guns and the cylinders online, your FFL dealer may be able to order them his at lower price and pass the savings
on to you.
Hope this helps.
Tecolote