I would think this could be repaired, but the cost of the repair is going to make it a no go.
First you have to chase the crack out completely by grinding.
Then heat the head to 400 degrees or so and let it soak at that temperature. This will help bubble contaminants out of the aluminum.
Heat to 400 as a welding pre-heat, touch up all grind areas while hot right before the welding to make sure its as clean as possible.
Tig weld with a harder rod (I forget the number) and make sure you have enough fill the first time.
Back into the oven at 600, bringing the temp down slow to normalize the head.
Now you have to do the machining, which will probably include decking the head because of warping, certainly new valve seat, and depending on where the crack goes you might have had to fill the spark plug hole completely with weld. So of coarse, drill, tap, and spot face the welded spark plug hole. You will also need to do some porting to clean up the runners and valve pocket.
When done, you have a repaired aluminum head that might or might not hold. The only for sure thing is you will have a bunch of time and money stuck in it.
I would either try and stitch pin it, which I am not even sure works on aluminum, or find a better head. Aluminum heads for these are not that rare, and a lot cheaper than a comparison Harley head from the same time period- plus you dont have to search out a correct date stamp.
Lee