Fabricate 4 off stems for the dual & quad wobble roller arms to U bolt to the chassis using 40 x 40 x 3.0 SHS and U bracket 3017(NZ). If U bracket 3017 is unavailable in your area/country, source a suitably sized U bracket suitable for fitting a 40 x 40 SHS section with a little clearance each side to allow roller arm to rotate.
Fabricate 1 off each of the MK3 stems and MK10 stems for fitting to the chassis sockets.
If MK3/MK10 rollers are unavailable in your area or country, substitute with a 3" (75mm) bow roller & 5 or 6" (125 - 150mm) cotton reel roller respectively.
Use stainless steel pins and split pins and either galvanised or stainless steel washers for mounting the rollers to the stems.