I just had a thought that, perhaps the 2-pulley electric PTO is off a 200 series John Deere. The setup of those machines is in a way that you need 2 different belt pulleys whether you want to run a mower deck, or if you want to run a front-mount attachment like a snowthrower. The inner pulley would be for a mower deck, and the outer for a snowthrower.
Or, you say the whole engine was replaced, so perhaps you have the complete engine and PTO from a Deere 212?
Just throwing out a couple ideas.
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'70 107 with k301 engine swap
'71 106 with 38" deck
'70 147
R with factory replacement k321, 42" deck
'61 Original with 38" timed deck
'63 70 "pinkie"
1863 with 54" deck
'46 Farmall H, '50 Farmall Cub
105 x2 (parts)