Looking at Z1s

I really love my 78 LTD but I am looking to expand to add another superbike of the era, a Z1.  I'm game for any year but the 73 is the preferred (but definitely open to nice 74/75), and BONE stock other than say a period dual disc front addition, oring chain, and/or a dyna ignition.  Still want the factory parts though for any deviations to return to stock if desired.  I'm hoping to start the looking at specific bikes journey in January and hopefully find one worth getting for summer.

It seems the value is putting it to a point where people are bitsa style piecing bikes together.  There's this bike on BAT that looks nice but has a lot incorrect:  bringatrailer.com/listing/1973-kawasaki-z1-900-24/

What advice do people have to get a nice bike and any sources or guides to help? 

I have this book and wonder what people think as well as other reference material that's good to look at:  www.amazon.com/Kawasaki-KZ900-KZ1000-Ent...x%2Caps%2C157&sr=8-1

I would love when I get serious to know how I could elicit the opinions of the experts here since a lot of you know these bikes super well and are invaluable!  I've helped people on Corvettes and Jags as has my dad, and I know how invaluable the consulting an expert enthusiast is great to get the right vehicle .  BTW this is my journey with a return to stock on my LTD:  www.kzrider.com/forum/10-new-members/621...rom-mi-78-kz1000-ltd

Welcome to the Z1 nut club!  As far as the BAT you referenced - run away from it.  In my opinion that bike looks to be a cobbled "restored to original" that's getting shuffled between opportunists (or scam artists). There are authentic nice originals still out there and accurate restorations by reputable people (some are members here), but be prepared to PAY for one.  The listing you showed sets off all the alarm bells! Most obvious is the speedometer - it's an aftermarket repro they're claiming to be original ND.  A bike like you are searching for will have a known history, BTW.
The book by Chris Rooke you have is a good restoration guide, but he does his restoring on a budget (his claim) and therefore will use repro or aftermarket parts. Nothing wrong with that.
If you can find a copy of David Marsden's book on Z1 Z900 and KZ900, it will give you a better background to recognize original bikes.  
Don't get discouraged, a Z1 that fits your taste is out there, but be prepared to do a lot of looking.  My Z1 taste is more of a hotrod bike, but there are plenty of members on KZR that are original bike fans, and we'll all be happy to help you find the right Z1, just ask.

Oh absolutely no question; thats a hodgepodge, I was using that as an example of the bits and pieces assembled bikes I want to avoid .

I just bought the book:  z1parts.net/original-kawasaki-z1-z900-kz...ers-guide-hardcover/

I don't mind some reproduction parts as long as the honesty is there and the pricing correct accordingly.  I don't want to pay all OEM and original money for an aftermarket or repop part containing bike that's worth less in terms of dollars.  That said, I really like riding these bikes and despite being 38 and not there for the original heyday, my dad was and loves these too and we like riding my bikes together.  He's owned a 73 Z1, 79 LTD, 69 CB750 Sandcast, and various other hot bikes in era.  That said, riding my much less fancy 75 CB750 is still a blast, my LTD is basically new condition, and riding both together is a lot of fun.

Yeah, that's the book I referred to.  You're right, that was an extreme example of your hodge podge point!  I've had my Z1 since around 1980 (I'm 70 now) and other bikes came and went over the years but always kept the Z1, it's my favorite.  I revived it a couple years ago when I retired and there's nothing better than a ride on a Z1. 
And Z1parts is a good source for quality Z1 stuff - an honest and reliable vendor.

Looks like a bargain compared to this POS currently for sale in the UK - (this guy states in his ads "priced firm not negotiable") remember this is Sterling so approx 6000 of your USD's !!!!!!!!!!!!!!!!!!!!!!!!!!

Don't buy it, Wookie!      ha,ha