Thinking about your project, how about taking a 1-inch diameter round stock Drilling and tapping the center to the same thread pitch as the crankshaft threaded hole. Then make an extension adapter to the length you need , assemble it with red Loctite on the threads. Then when you have it tightened as much as you can you will carefully take a cutting wheel and make a slot for a full-length key to go between crankshaft and new adapter and pulley.
I think this should work without any issues and make your project easier.
You could also take a 1-inch diameter round stock and drill a hole through the center, then have a keyway cut onto it, and then have a long Bolt through this new piece and bolt into your crankshaft. This would make it longer and be able to allow the pulley to slide on it. But machining would have to be perfect as it will be turning 3600 rpms. Just another idea to make the crankshaft longer.
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