I went through all the "tech library" looking for parts for my 1975 GT80. There is nothing available. Does anyone happen to have part numbers for the turn signals and headlight and brake/tail light assembly. Also, the brackets for the turn signals were "shaved" off, so I need suggestions on how to fix that dilemma.

Partzilla. They'll show you the part numbers you need.

www.partzilla.com/catalog/yamaha/motorcycle/1975/gt80b

Unless you have the MXB then use this link.
www.partzilla.com/catalog/yamaha/motorcycle/1975/gt80mxb

Thanks Jack.
I'll take a peak at Partzilla.

When you checked the VIN... what did tables say? If no turn signal brackets on frame it might be a GTMX with the 367 prefix.

Speed & Sport has 3 in stock of the steering crown with turn signal stand offs. $89.25 ea
I have one I can sell off 74GT80A, same part no. Not sure if it's silver or black, would need to dig it out to see.
If your interested send me a pm, we'll sort it out.

Well, went on Partzilla. Nothing I need/want is available.
Guess I need to look for a "junk" bike & scavenge parts off it.

My vin starts with 393

Also look at the CMSNL website - very similar to Partzilla, but with, I think, more photos of parts.

Both Partzilla and CMSNL will show which other models (of the ones that they hold parts manuals for on their respective databases) had those parts fitted. Also, familiarise yourself with exactly what the parts you need look like, as a lot of parts on fleabay are mis-described (though usually not deliberately). Armed with this knowledge, you can widen the scope of your search for parts.

Some of the things you mentioned are available on e-bay. brand new tail light bracket $135 for starters. So what you need to do is write down the part no you are looking for and punch that into the search engine on e-bay and see if any are any for sale.
Also www.speedandsportinc.com are a good source for O.E. parts.
Patience is a must with the search for parts. It's not an instant gratification type project when doing an restoration.
I spent 2 yr's doing my 1st Enduro and learned a ton of stuff about the parts market. You can get screwed easily on prices.
And a parts bike is certainly a good idea if what you have to start with is lacking. The mini enduro's are a hard to find bike depending on where you are located. There is a facebook page for those bikes, you might get some help there. I can tell you that when I mentioned making an MX out of my 74 that folks where hot after what parts I might offer for sale. I haven't started the project yet. What you see in the pic above is what I have. Also the 1st piece I swapped out was the steering crown your looking for. I'm not looking to make a killing on it, I don't play like that. I'm here to enjoy what all these guys have going on, to share the fun & learn from some of the best.
GOOD LUCK and to the site.
My 1st project started in 2014 and finished in late fall of 2016

Oh, yes. I've looked at the pictures, says it fits "these vehicles", ordered the part(s), ended up sending back because they are way way wrong.
Ugh.
The resto shop that got my 80 running ordered the tail/brake light assy from the YAMAHA site. Coming straight from Japan (supposedly). Waiting. Waiting. Waiting.