Wiring diagrams for a Dayton winch #3VJ74 seem to be rare online and not even Google Images could produce such a diagram. The best diagram available appears to be the one on fixya.com, which I've reproduced below:
As you can see, this is the wiring diagram for a Superwinch X9, but the fixya.com user who provided the picture believes the two makes are almost interchangeable, so you may be able to work around it.This aside, there are lots of Dayton items for sale on eBay, so perhaps one of the sellers could be persuaded to reproduce a copy of the manual for you.
You could of course contact Dayton themselves, but I have been unable to find their customer service number online. If you ask at your nearest Dayton stockist, or consult the packaging of a Dayton item at the store, this might help you further.
Finally, you could try gemplers.com/docs/manual, which offers PDFs of some Dayton products, you may be able to find a diagram for your winch there, or you could ask around in a forum like homeappliance.manualsonline.com.
I hope this is of help you, and good luck with the winch!