Vitaly Klitchko - WAKO fullcontact World Champion in 1991, Paris -
Regina Halmich - WKA European Champion around 1993
Troy Dorsey - WAKO, PKO, ISKA multiple World Champion 1983 to 1993
James Warring - WKA World Champion (beat Klitchko in kickboxing)
Khalid Rahilou - WAKO and ISKA World Champion 1987
There were a lot of good fullcontact fighters and kickboxers moving into boxing and just short of title shots like Howard Jackson, Rick Roufus, Marek Piotrowski, Peter Cunningham, Skipper Kelp, Przemyslav Saleta (he beat Klitchko in kickboxing, ISKA).