I hardly dare to ask the obvious: Did you try MiniVMac for running your app?

http://minivmac.sourceforge.net/doc/download.html

I found MiniVMac and FusionPC best for running the very old stuff, if you dont have a suitable vintage Mac.

FusionPC will need to be hosted in DOSBox,(or in WIN98 or lower on real hardware).

As far as I know there is no DOSBox for Classic MacOS, but other solutions may be floating around.

http://www.dosbox.com/download.php?main=1

http://emulators.com/download.htm#MACINTOSH