I am willing to bet that it won't make a bit of difference to either rifle.
I saw hundreds of those rifles come in without bolts and then a couple of cases of bolts cleaned up and installed into those rifles.
As far as strength goes, I am willing to bet those Chinese Chiang Kai Shek Mausers are as strong and safe as any others.
I have personally built up several sporters on those actions. They used to be available by the 10 pack without bolts or barrels but otherwise complete.
The only thing that may be an issue with some of those old girls is if the lug recesses have been set back in the receiver. This can be a problem with any Mauser, even with matching bolt.
Don't let the beat up appearance of the rifles fool you. For the most part, it is only skin deep.
They are likely chambered for the 7.92x57 Mauser cartridge. If you want to make up a quickie guage, add a couple of thicknesses of Scotch tape to the back of an UNfired cartridge. Take the firing pin section out of the bolt and see if the bolt will close on the inserted case. If it won't close or is just able to by crushing the tape that is a good thing and you don't have excessive head space. The chances of not enough head space are 1 in a million.
By the way, I have never seen a stretched Mauser 98 action. I have seen them with lug damage and lug recess surface set back though.
Another thing you may want to do is magnaflux those receivers. I have never seen one cracked but who knows. You can do this yourself with some grinder dust and a small horseshoe magnet. If you find a line of dust has formed, put a couple of drops of Varsol onto it and then wipe it all off. If Varsol weeps out of the line, you have a crack and the receiver should be scrapped or made unserviceable.
