Frank
What I have been trying to explain to folks out there trying to get these multi ratings and IR done. There are lots of schools out there that will train in multi engine airplanes and they do it everyday. It sounds crazy but it is going to be so much simpler to just finish the task in a standard twin that is available at almost any school. Then see what the insurance requires for your Skymaster. I guarantee it will be much easier this way then going about it the other way. It's like trying to enter through the back door instead of just walking through the front.
Call your closest flight school and get it done. That may present the next problem is waiting in line at the school as these schools are so busy. Everywhere there seems to be a shortage of CFI's. You could always go to a school like ATP that may have multiple locations and may be able to do you quicker.
Or maybe call these guys and tell them your story
http://www.337skymaster.com/messages...ead.php?t=4643
http://www.337skymaster.com/messages...ead.php?t=4631
http://www.337skymaster.com/messages...ead.php?t=4536