Looked all over, haven't found any hint of this being done.  The Marksman started out as air force surplus A-26 Invaders (for part of its career it was designated B-26, forever confusing aviation enthusiasts because there was also a B-26 Marauder, which was a totally different aircraft).  On Mark's modifications were extensive, and from what I understand they eventually came to the conclusion it would be just as easy to build their own new type.

jrbirdman wrote on Nov 17^th, 2012 at 9:34am:

That is where I got mine and the Marketeer.

by the way, my dad found a real one in Chicago a month ago, posted some pictures:
/yabb?num=1349558378