If I remember correctly they had a 1964 Mustang shipped over from UK to Koni/Netherlands, I will need to find again, which one it was.
Acc to this article (thanks to Arjan Nugteren/Dutchmustang.nl) Koni developped a variety including a 6 damper upset (2 guide the rear axle better) (Autovisie 30/1965)
On sale for 325 dutch guilders.
About the export brace missing - true my 68 T-5 that was originally bought by a US serviceman had no export brace installed. It is assumed that PX ordered cars for servicemen could be done that way, as they were thought to be brought back. I have seen not to many T-5s without export brace, maybe one or two. In most cases owners think it is not a real T-5, so they do not register.