Partzilla has parts diagrams with a cross-reference. I would compare the frames, crankcase set, mufflers, etc.
From a quick check, without verifying the info at Kawasaki.com, the 2002-08 VN1500/1600 models had the same crankcase.
When relying on the x-ref at partzilla, I always double-check at Kawasaki.com
to make sure the donor model part is the same.
Vulcan gadget. The vulcangadget fixit page has a bunch of info for the 1500,
but I don't know if there's anything about an engine swap.
1981 KZ650-CSR. Competition, Sports & Road.