Not a big deal Mike. Ken here (you probably know him) has a 300 H&H pre 64 model 70 that was built on a std action and he says it works just fine. It's hard to find mounts that don't hang over the ejection port because of the cut-out in the back and small mounting surface. I believe my talley lightweights hang over a bit as well on my 338...
The Leupold PRW's were pretty good on my 375 and were almost flush with the rear of the port:
That cut-out in the rear (and front) of the loading/ejection port helps for both loading and ejecting. However, some say it wasn't really necessary. Even for the long 300H&H and 375H&H magnums... If your rifle works
flawlessly, I wouldn't sweat it...