These guns may not be importable into the US. If they are it will be expensive to bring them in for sale

They will need an approved ATF for 6 to come in. It has been ATF's policy in the past to treat Mausers with left rail cartridge cutout as military surplus. No cut out they should be allowed

I have exported fire arms from SA in the past-twice.

It took me some time to get an export license from SA, then the guns must be sent must sent air freight to the US. I used Classic Arms in Witbank as my export agent. They charged a fee. There was also a courier from Witbank to the freight forwarder, with fee The guns had to becrated to be shipped, another fee.

Once these gun arrive in the US, since they would be coming in for sale and require import licenses, and have a high value they would be required to make a formal custom entry paying brokerage fee's and possibly duty.

A US dealer will charge additional processing fee's for sale and transfer.

Best way to sell these into the US, is for a US person to buy them and do a personal importation. After the US ATF Form 6 is approved and after the SA export permits have been approved, fly to South Africa for a trip or hunt and bring the gun back to in baggage a personal importation.

Fees still due, but there are some exemptions. No airfreight.