Thanks so far for the comments, I appreciate the time and effort it takes to dig this info up. I know all about digging up the facts as I have a copy of Roy Dunlaps "Gunsmithing" book, A copy of the de Haas "Bolt Action Rifles", a copy of "Rifle Smithing" and a couple copies of "Home Gunsmithing", amongst others. All in all, it's turning into quite the collection of gunsmithing books, and this is (in part) the driving force behind wanting to talk to someone who's done this sort of conversion. In all of the before mentioned books, plus may magazine articles, a majority of the writers state that although the Jap actions are among the strongest and safest to come out of WWII, they're often overlooked as a basis for a sporter. Part of the reason for this because of a misplaced bias that people like Hatcher, Ackley, and MacFarland (to name a few) have worked hard to dispell. The bias (of course) being that the Jap actions were all made of pot metal and were junk. Another reason, and probably the main reason why Jap actions are passed over, is because of the fact that their barrel threads are not standard, and because of the complex breeching. It takes too much time to match the original breeching if the original barrel is set back a few threads, and if a new Bbl is used, then there is the dual problem of matching the threads AND then the breeching. It's much easier to rebarrel a M98, or a Win70, or Rem 700. True, all of it.
One of you mentioned cost. Surely finding a 'smith that would even attempt the work would be a difficult task, and it would take a really BIG pile of Komrade Klinton's new quarters to pay for it. But I have a few aces up my sleeve. One: I have a source of a type 38's and 99's that I can have my pick of for a really decent price. Two: GPC sells Bbl blanks for a decent price ($30-40) last time I checked. Three: Any after Mkt stock made for a Mauser can be modified (inletting changed, Glass bedded, etc) to suit. Four: With the exception of the chambering and throating, and quite possibly the Bbl threading, all of the other chores are well within my ability, and my labor is free. I have access to machine tools, and expert help if the need arises, I have better than adequate welding experience, and my other hobby is Cabinetmaking - so the wood work is a breeze.
You see, I want something unique, a Sporterized Arisaka, in a custom caliber, like .257 Ackley Improved. I really don't have the means to pay someone else to do all the work, and I don't learn anything that way. I am at heart a Tinkerer, and I suspect that all of you are also, or else you wouldn't be here at this site. So I am really interested to see if anyone out there has actually done the conversion, so that I can trade notes, and possibly avoid any pitfalls along the way. Once again, thanks for the info to date, and thanks for taking the time to answer. Unkel Gilbey