Finisher,
I think it would have been a negative thing for your to have spent $650 for a re-worked Ishapore. (Unless the scope on that gun was worth $350). If you are really interested in the Ishapore route, I think you would be better off buying one at a gunshow, at the lowest price you can find, and shooting it for a couple of months (without spending a dime on modifications), to see if you like it or not. You may well find that the platform is totally unacceptable. (I could be wrong, but I think that if you install a receiver sight, then you may not be able to use the stripper clip fixture.)
It is not hard at all to find 7.62 Nato ammunition. I think that several ammo makers manufacture and sell mil-spec 7.62 Nato. I would thing that the UMC brand certainly has it. Buying surplus 7.62 is often a very hard way to go. For example, a few years ago, there was lots and lots of great looking surplus Nato ammo released and sold from Argentina, in dark greeen plastic battle sleeves. The gunshows were full of the stuff. Unfortunately, it turned out that this ammo was loaded "overly-hot", perhaps to better work in heavy machine guns, and it would shut down bolt action rifles. The case expanded so tight that you could barely open the bolt. Many broken extractors and problems from this. Extreme signs of high pressure.
Although the Ishapores have a detachable magazine, it is a fairly crude magazine and it isn't easy to just snap on and off. The overwhelming majority of folks I have seen shooting these are loading them from the top, using stripper clips or one by one. Replacement magazines are out there, but these seem to be hit and miss as to function.
I am not a fan of the new Ruger Scout, but many folks swear by them. I hate the long, single stack magazine, especially the way it hangs down. But, please read asap the post by Swampman on his new Ruger,, especially the new magazines available for it. I believe he said that some company is making 10 rounders, that are stagger feed, that will fit the rifle. This kinda changes everything. (Look in the Bolt Action Rifle section, under My New Ruger, and read all of the comments.)
This is just my personal opinion, but if I were building a Scout, I would buy a Howa 1500 rifle, in .308, with the full length, standard weight 22 inch or 24 inch barrel. (A used one in vg condition would be fine.) I would then have the barrel cut and crowned to 21 inches. I would then install a quality synthetic stock. The big news for these rifles is that Howa now sells kits, to replace the blind magazine at the bottom, so that it will accept 10 rounds magazines, which I believe are staggered magazines. From what I have read, these work great and people are very happy with them. If you look on gunbroker, you will see people selling the brand new Howa 1500s, with this kit and a 10 round magazine included.
I also think that the new Savage 111 Hog rifle, in .308, would have a lot going for it at a Scout platform. The great part about it is that you could add the stuff you want, one step at a time, instead of trying to do it all at once. At present, I think it has a 5 round blind magazine. But, I also think there are conversion kits out there, perhaps made by Savage, that let you convert to a detachable mag. These are currently 5 round, but I would have to believe that higher cap mags must be on the way.
If you are simply wedded to going with an Ishapore, thenI personally I would buy one of the full size rifles. You can still find these in shipping boxes packed in grease from the arsenal. (Used, though). Often, they are cheaper than the carbine versions. Assuming you like how it shoots, you could then shorten the barrel to whatever you like, and customize it one step at a time. In all honesty, though, I don't think that many folks are using the Ishapore as a serious Scout platform.
As for converting it to 7.62x39mm, I can almost guarantee you 100% that you will have feeding issues. The outer dimensions of the Nato and Russian cartridges are significantly different. The Ishapore was designed for the Nato round, and often it does not even feed that round very well. Go to Google, and search "problems Ishapore rifle."
Hope this helps.
Mannyrock