This is a very common problem with this conversion. After spending $2,300 with my gunsmith for this conversion and other items, I received my mauser back, after 10 months, untested for feed, and jamming on every 4th or 5th round. Absolutely incredible that they don't carefully check this before it leaves the shop.
When I took it back to the smith, he acted like I was some sort of trouble maker, and begrudingly took it back for more work for free. Eight months later, I got it back, and it worked fine. He had done the following:
1. As recommended in almost all old gunsmithing books, he had welded two very small metal rails running vertically on each side, on the inside of the magazine. The purpose of these rails was so that when loading the shorter .308 rounds, the rounds would be forced to be pushed to the very rear of the magazine, with the shoulder of the rounds being tight behind the rails. The rounds would be then held in place there, because the rails lined up with the shoulders and none of the rounds in the magazine could slide forward in the magazine before they were being pushed out of the top of the magazine by the bolt. This is mentioned as being very important in the gunsmith books, because otherwise, if the rounds are free to slide back and forth in the long magazine, then they will do this during firing of the rifle, and carry, and they will all be lined up differently in the magazine as you try to work your bolt.
2. He had obviously exerted some great bending pressure on the lips of the magazine, as I could see various tool marks.
After these adjustments, all rounds fed and ejected perfectly.
If I had to do it again, I would:
1. Make a spacer to take up the front part of the rilfle magazine, by taking a magazine from a .45 pistol or other suitable size round, making a perpendicular cut across the top of it, and then cutting it downward through the length of the pistol magazine. Obviously, the original width of the pistol magazine must be such that it will slide down into your rifle magazine, and be fairly tight.
2. After doing step 1, before sliding the spacer down into the magazine, I would use acra-glass gel to make a feed ramp that would go on the top of the cut magazine. It does not have to be a steep feed ramp. Just enough to gently lift the nose of the round up to the level of the barrel throat.
3. After steps 1 and 2, then slide the spacer in, but do not fix it in permanently with accra-glass or welding etc. Test the feeding over and over to make sure that your ramp works right. Use files and sandpaper to adjust and smooth the feed ramp. Once you get it right, carefully mark the proper depth of the spacer into your magazine, pull it out about half way, put some acra-glass jell on the sides, and slide it back down in the magazine to the marked depth. Then let it dry.
If you don't want to try the foregoing, then here is the easiest way: See if on a web sites os used parts etc., and find were you can buy the entire bottom metal from a short round (.308 or .243) Interarms Mauser Rifle. (They made thousands of these in the Mark X model, as well as other names such as the Viscount, and the Muskateer) The basis of these rifles is the Yugo model 98 mauser rifle, and I believe that with some very minor fitting, the bottom metal would fit fine on any other classic model 98 mauser. (I think that the hole spacing for the guard screws differs by a couple hundredthss of an inch from the standard model 98 rifles.) These Interarms rifles feed very well. I can't remember whether they have placed the spacer at the rear end or the front end of the magazine.
I don't think that you are going to find the part you need from an Israeli converted model 98 rifle. These conversions were done in the 1950s and 1960s in an Israeli arsenal. Being war guns, they are also pretty rough. The only way I think you would be able to get one would be to buy an entire converted Israeli rifle, which I think you can get for as little as $125 in poor shape. But then, you are stuck with the receiver.
Hope this helps.