If you can do ANY fabrication, AKA operate a drill and a hacksaw, you an MAKE a starter mount "not that hard." Get some plate steel, say, 1/4" but make sure it will clear the flywheel first. Trial fit the starter in the block and make a gusset out of plate. Just drill it to fit, cut and hack. I use the mid plate out of a scattershield.
I do not have any provision for supporting the starter nose, but figure the few seconds of crank time, it's worth the gamble, and use an old starter just to be sure. So far I've done this on maybe 5 used engines, and have not broken a starter yet.
Some guys have even torched up an old torque converter so all that's left is the front face and starter rear.