(I'll preface this by saying that though I do have a Yugo M48A, I haven't sporterized it. I have however sporterized a Turk M38 Mauser as well as a Spanish La Coruna Mauser - don't worry both were well beyond collectability before I started messing with them

). I've also got a sporterized Swede M96, though I bought it sporterized rather than having it done myself.
For inexpensive stocks you can find a Boyds stock for the M48/M48A for about $75.
Don't know if the RIA Sportsman works out better (the RIA has the military step barrel channel which you'd need unless you rebarrel), but the JRS Classic was a severe dissapointment for me. It's sold as a Mauser stock, but without removing a LOT of wood from the stock, the cocking piece will hit the comb as it comes back. I've got a sporterized Turk Mauser .257 Roberts with one of these and that part of the stock looks pretty much chewed up. Overall fit was not good either. Mine has a lot of gaps between the wood/metal where there should be none. I'm seriously considering getting a Richards Micro-fit for it. They look pretty good with the Rosewood tips, and I've heard that they're of better quality than the Boyds stocks.
I can definately second that recommendation for the Bold triggers though. Excellent triggers and very resonalbly priced.
Also, there are serveral guys on the net that will forge a bolt for $35 or so. Excellent deal as long as you find someone who will do the job right.
BTW, pics of my sporter Mausers:
http://www.winterfairy.com/guns/turksporter1.jpg">Turk Mauser in .257 Roberts
http://www.winterfairy.com/guns/spanish_mauser_sporter.jpg">Spanish Mauser Sporter (I've had it drilled and tapped since this but haven't updated the pic yet)
http://www.winterfairy.com/guns/swede_mauser.jpg">Swede M96