Zorroz,
That is the exact bike that i used as a baseline. The rear swing arm is the missing link, but that is currently being worked on. Interestingly, the pipe that was fitted to the bike gave the bike an even stronger top end, something the 84 RM125 never needed. Apparently the bike was all but un-rideable on hard park but was at home on the Euro sand tracks.
Some say that pound for pound, year on year the 84 RM125 was the best RM125 Suzuki ever built. I dont particulary care either way, but i do think that it was one of the best looking bikes of the era.