I happen to have a 413 industrial and the 727 that came with it out of a 73 winny. Ran great before I took it out. Just in case your interested. I'm not using it.
That one-off 413 industrial is just as hard to get parts for as the 318-3 but at least it has more power. If you're going to do a conversion, you might as well put in a 440 and be done with it.