If I remember correctly a company by the name of Kustom Truck in Coos Bay, OR sells a complete engine swap package to put a 12.7L or 14.0L Series 60 in the Cascadia platform. The last I looked the kit was in the $7,000-$9,000 range and all you needed to provide was a long block of your choice. Might be worth giving them a call to see what their package consist of.
Have you talked to Harrison or Fitzgerald Gliders to see if they could point you in the direction of the resources that you need to perform a swap of this manor? May be worth the phone calls just to see if you could gather some useful information before you spend a boatload of cash on a swap that won't work.