BTW, number and position of locking lugs are, by themselves, no indicator of a gun's strength or safety. There have been high pressure cartridge guns made with rear locking lug bolts. The M61 Vulcan, in 20mm, uses six bolts, one for each barrel, and each bolt only has ONE lug!
Any properly manufactured rifle, in its original configuration, will be safe to fire with the ammo it was intended to shoot.
The Ishapore 2A was properly manufactured for the 7.62 nato.
Therefore, it is safe to use that ammo in that rifle, provided the rifle is otherwise safe.
Tom raises good points, but I'd like to clarify several things.
1. The M61 Vulcan is not firing with the breech directly in front of my face.

I do agree most emphatically with you that the results are what count, not the specifics.
2. We don't know what these rifles were proofed to, if they were in the first place.
3. There are dimensional differences between 7.62mm and .308.
4. There are considerable (11,000 PSI, or thereabouts) differences between the nominal maximum allowable pressures of 7.62mm and .308.
5. If the rifles could handle the higher pressures and smaller cases with no problems when they were new, that in no way guarantees that they will now. Receivers can and do stretch with use and increase headspace. (Particularly when one is routinely running ammunition that's up to 11,000 PSI above what's normal.)
6. While I do not have firsthand knowledge of 2A's grenading, a Google search of the rifle will likely turn up reports of .308 head seperations on the first page. Yahoo! did, anyway.
7. India is not a member of NATO and may have a different opinion of what NATO compatible means. The prosecution presents Exhibit A, the 1A SLR, which is not compatible with anything but is still, at least technically, an FAL.
None of these by themselves mean much. Taken together, they tell me to use 7.62mm surplus and to take it easy on the handloads. If I'm overly cautious, it's because I've had a rifle pop on me and I have no wish to repeat the experience.
If I were a betting man and I had money riding on it, I'd bet on a given 2A handling years of the hottest SAAMI-spec .308 loads with no problems besides what happens to the brass. Why risk it, though?
Put another way, I know what 10mm can be safely reloaded to according to SAAMI, but do you think that I really want to run that through my Glock? Sure, the pistol's rated for it, but the brass dies an early death and my margin of error is basically nonexistant; if the diopter on my powder measure slips and I gain a grain or two, it's going to pop. I'll give up the 100 FPS for peace of mind if nothing else.
This is coming off like I'm trashing the rifle. I'm not. (As I said earlier, I want one, and if I hadn't broken a tooth today I'd be shopping for one this weekend.) My point is simply to use a bit of caution. Milsurps carry no guarantees and when military rifles fail in use -- and they do, trust me, they do -- there are no lawsuits and if the number of catastrophic failures is within someone's idea of an acceptable limit, the problem is not even corrected immediately.
Be careful. Just saying.