Hello Drew and welcome to the forum:
individuals in the past have done this mod, some easy some difficult.
It really depends on your availability of parts, or on the worst case it would depend on how fat your wallet is.
In quoting recent eBay auctions:
A clean KZ seat can go from 500.00 to 800.00 bucks.
Tail pieces can be reasonably priced.
Lighting can be pricey.
I would guess the fork lobes, and headlight, along with the seat to be the priciest group of items.
A new NOS fuel tank (They rarely come up for sale) can be 500.00 to 1000.00 bucks. A used one much less. However the used tank will need to be refurbished.
For my Z1R, I recently paid 1,000.00 for an new fuel tank.
Before you do all of this work, thoroughly evaluate the bike your possibly spending this money on. i.e.
Is the engine solid.
Are all of the electrical components worth salvaging?
This assumes you may need to do a frame off refurbishment.
when looking for a bike, don't just look local.
Go to
www.yakaz.com for nation wide craigslist searches, to hopefully find the bike you are looking for. You may even be able to start with a good condition KZ.
They are out there, be patient and keep looking.
Keep us posted.
Todd.