I've only ever had one pass through my hands...it's for me sorry.
But. I can recomens this.
http://www.mts.net/~lewman1/
Somewhere in there for about $4 is a Destroyer kit. It is a cast of the head to swap out on Thorbuster IM and a chest piece. to put on him as well. Then paint the whole thing and you got a Destroyer.
I've never bought from him personally but FTB Swears by the guy.
I wish they offered a tutorial of how to switch heads...there's no universal peg.