OK, decision has been made.
The primary choice is the Cummins R2.8 repower kit. Managed to pry loose just enough information to be 90% certain it will fit.

If Cummins stumbles and doesn't release the kit on time ( First Quarter '17), 5 weeks max, then the Plan B will be the Boss 302 290/300hp.

Now the work schedule can be planned around waiting for final engine information.