Thanks for your insight englishman_ca. Yes, I already understood that creating the proper pistol grip would probably be the biggest hurdle on this type of mod. I don't have a gun for this project yet but, I had my eye on one that was in pretty good shape and selling for only $150. So, I'm not going to be putting a whole lot of money into it. I don't mind doing the work, in fact, I'd probably enjoy the challenge. I was a custom machinist for 35 years, although, I don't have any of those machines to work with now. It just sounds like a fun project to try, even if I don't end up with a usable pistol. I can still hang it on the wall and, have a good laugh, every time I look at it.
My thoughts about legality were along the same lines as yours but, lets face it, any time we talk about legalities and antiques there will always be differing opinions. The fact is, the only opinion that matters is, that of the attending LEO, if I should happen to encounter one, while out in the bush with my sawed off antique gun. Heck, even if it wasn't sawed off, there is no guarantee that things would go my way.
Yes, I will be checking out the pistol grip, on any long gun, to make sure that it gives me the best chance of doing this kind of mod. And, like I said, I'm not going to be putting a lot of money into this. It's just a fun project and, if it works out, that's great. If it doesn't I still had fun trying.
infideleggwelder; I don't think that there is any legal minimum length for this kind of thing. It's not like with shotguns, where there are definite dimensions to adhere to. These are antique status guns I'd be working with so, they are considered non-firearms, unless used in commission of a crime. But, like I said before, there's only one opinion that matters and, it's the same regarding any antique guns, not just a modified one. I have other antique handguns and, I have an FRT for them but, that still doesn't guarantee anything.