suspension conversion for ke125

i'm a real newbie here guys, i hope you could help me. i have this 1978 kawasaki ke125 at the old garage and decided to fix it. fortunately it still runs pretty good,i go trailing on weekends with it and sometimes do motocross(at avery low level of course). it has dual shocks at the rear and i find it too hard to ride in long trails.and i'm planning to convert it into a mono shock. could you guys give me some idea on this,what suspensions will fit or something about the mounts of the suspension?