How to tell how ORIGINAL my bike is?

[jdsmithinc]

Ok guys, I have my 74 Z1 running and riding like a dream other than the occasional backfire on decelleration. I have been really looking at it and want to know just how original it is other than the obvious 73 model engine on it. It was built 08/73, and is titled as a 74 (clear and in my name). I had asked a while back about the frame and engine numbers and this is what you guys came up with for me. My next question is how to tell if the tank is original? I just sold an original tank on ebay that was on a 75 Z1. The emblems screw holes were 5 1/2 inches apart. The ones on mine are a little bit closer, and the emblems are smaller. I hope I didnt screw up by selling that tank!! My other question is, how much difference is there between 74 guages and 75 guages? I fitted a set of guages from the 75 on it as I didnt like the little bitty chopper set that some idiot put on it. The original mileage of course is unknown as the little custom crap guages read 3,400 miles. The ones on it now read 28,000 some odd miles. The rims I am assuming are original, the side covers are also original and I am missing one of the emblems. I just bought a stock handlebar that should arrive soon, as well as the guage idiot light cover. I had to do a little doctoring to the wiring to make it look a little more crisp. I found a set of original turn signals front and back. It obviously doesnt have the original paint. How much does that hurt the value? It looks really nice but does have a few flaws here and there. I have actually thought of repainting it to the original color. How much would it hurt to strip the black paint off the 73 engine? I know I am bouncing all over the place with this post but I didnt want to have 15 different ones sorry. I guess it all boils down to what a realistic value would be for the thing.
Also note that I fitted a kerker 4 into 1 header and pipe and took off that black THING that was on it. By the way how do you guys like what I did with the rusty old shocks that I found? It at least matches the paint!!