Just finished doing this same conversion but in a GU, There is no need to chop up the engine mount bracket, just change the bracket on the engine side instead of the chassis mount then no eng cert required. Swap over your oil pressure sensor and speedo sensor out of your rd28 box into the td42 box this will keep your speedo correct without changing clusters. I'd go for the silvertop there a tuff donk and then upgrade to a dc3 or dc6 pump depending on your desires. Then all you have to do is chop up all your wiring and reloom it all so everything works like factory.