p.s. what do you mean by saying i need to buy a threaded barrel on the front end? You talking about the muzzle end or where it mates to the reciever?
I can't really speak much about buying an aftermarket reciever. Starting with one really drives up the price substaintially and I've never had that kind of cash to work with. I would suggest one thing, though. I didn't realize you were starting your projects with the carbines, but think that's a sensible start. If it were me, though, I'd make it a point to shoot several bricks through each of them just to shake them down and to determine the personality of each gun. Yes, they do all have one and few are similar. You might find that one is a great shooter and just a few choice parts is all it needs to shine, whereas the other is a dog and might be a good candidate for a virgin reciever. Keep in mind, a person can get carried away with upgrades on these things and wind up with so much in them that they are basically an heirloom item afterwards. The sky really is the limit when dealing with these. That said, some of the cosmetic upgrades are really elegant and probably more than worthwhile to some people. I'll certainly give them their due. A couple of members here own very nice looking 10/22s and I'm sure they have quite a bit in them, but it does show well. I'd almost be afraid to shoot some of the customs I've seen and that's just not for me. I'm not a collector, so a gun that I'm hesitant to shoot is a fairly worthless item to me. Sounds like you're on the right track, though. Just don't rush things too much, or it'll wind up costing you in the long run.
About the barrels, I was trying to point out that I don't know all that much, either. I've done some customizing, but nothing spectacular and most of mine was limited to off the shelf parts. If I understand things correctly, I believe you can buy threaded barrels that screw into the reciever. Never seen one and don't really understand how it works, since the stock reciever isn't threaded, but there has to be a way to mount them. They're supposed to be more accurate on a bedded stock, but that's about the limit of my knowledge about them. But, yes, there can be threading on both or either end. If you plan to suppress, you'll want to go ahead and order yours threaded with a thread protector. Additionally, if you plan to install a flash suppressor while waiting on a can, you'll want to order one with the same threads as the barrel. They come in several thread sizes and without threads at all that just crimp down with an allen screw. These are all just things that need to be well thought out or you'll find these things twenty and fourty dollaring you to death. Research and buy the right items the first time and you'll save a bunch. I'll bet I've thrown away several hundred dollars worth of useless junk I've bought simply because I didn't do my homework.
Anyways, I'll be interested in following your progress and, if you run into any problems along the way, happy to try to help you find the answers. Once you get started, you'll probably be finding more folks interested in your progress, because I suspect most of us here would like to do a custom build on one. I've seen quite a few that I'd have to rate as outstanding. About all I can afford to do is drool over them.