a+ used to make the set-ups, and probably a couple others. i have even heard you can use a pitbike frame but need to get some triples machined. i have been looking into this as well, cuz i would love to do my 70 up suspended. do a search you will come up with a few threads on this subject.
1985 KXT 250 Tecate - kx cylinder, kx ignition, bassani headpipe, answer silencer, v-force reeds, 38mm airstyker carb, +2 franks swinger, raptor rear shock.
1996 YSF240 Blaster - maxxed out!!!
Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting "HOLY SH-T, what a ride!"