If you've got the ball on the flywheel cleaned up and painted, it should be a simple task to turn the flywheel until the ball aligns with the pointer and check to see which spark plug wire the distributor rotor is pointing toward. It should be #1 or #6, as the engine turns twice for every turn of the distributor. You can use either spark plug with a strobe light to set the timing. The flywheel bolt pattern is almost, but not quite idiot-proof, as the bolt holes are not perfectly spaced. A sufficiently persistent idiot could probably install it wrong by not using all the bolts, but there would also be a massive oil leak through the hole for the missing bolt(s) as the bolt holes go all the way through the crankshaft flange and a leak can bypass the rear oil seal if they're not all there.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!