The Indian 2A and 2A1 rifles are not hacked together. These rifles were made with a higher grade of steel than the earlier Indian SMLEs made in .303. These two rifles may the best permutations of the greatest bolt action MBR ever made.
Yes, the Israeli .308 rifles are C&R. There are several common versions. You have the recycled Czech VZ24 receivers that often have the Czech rampant lion on them. I have seen Israeli .308 rifles made from recycled NAZI-marked K98k receivers (and many with WaA-marked parts). Also, you will find the FN-made Mausers (intermediate length actions) that are in .308. In the 50s and 60s, these rifles were rebarreled into .308. Virtually all of them are on 50 year old receivers, so they are unavoidably C&R.
As for the effect of modifications on C&R rifles.
If the rifle's receiver (the "legal" part of the firearm) is at least 50 years old, then it doesn't matter what modifications you make to it as long as they are legal for any firearm.
For those C&Rs that are less than 50 years old, modifications can cause them to lose their C&R status. For example, a C&R missing parts is considered a C&R. Century has shipped many thousands of UFixEms in this condition as C&Rs without any legal problems. It is no secret to ATF that CAI does this.
However, when you start adding non-original parts to a C&R less than 50 years ago, you begin to change its status. If you take a GEW98 and replace its barrel in a non-original caliber but maintain its outward appearance, you are likely getting into an area that the ATF really doesn't care about. However, turn a younger C&R into some sort fantasy sporter, and it won't be C&R anymore.
The ATF has many rules. I imagine they have many more than they have the time, resources, and interest in vigorously enforcing. Minor changes in C&R weaqpons and the now ridiculous enforcable 922(r) are two of them.
I am not advocating breaking any laws. I'm just saying that flauting the law will bring you grief while minor statutory infractions are not worth losing sleep over.
Guys, 9-11 changed everything.....and I mean everything.