All the PTO drives on the cluster gears I've seen had straight cut gears. Trying to mesh a set of helical gears to engage a PTO would be difficult, if it could be done at all. That's one reason a transmission is noisy when the PTO is engaged. On the big rigs I've worked on, sometimes there's an adapter with an idler gear between the main box opening and the PTO, especially on one that can turn both directions to run a winch, etc.
Jerry

Edit: I just found a crash box PTO on Ebay from a 1937 4 speed. It looks somewhat different that tne one for a 420, so I bought it.
Jerry

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