Purchase the resin conversion here: http://www.e2046.com/product/RX-78+High+Mobility+Type+Conversion+Parts/2314/
Pictures here: https://gemr.com/user/prime92?utm_source=Sam&utm_medium=Social&utm_campaign=Prime92
This resin conversion set is for the MG 1.5, but I don't have it. So with a bit of modification, I got it to work with the 1.0 version.