Got it. And yeah i get the point you made, why worry about the frame if the motor is shot as well?
I have some ideas on the frame (yeah these are longshots but bear with me)
1- find and mod another datsun frame
2-build your own tube frame (this one is the biggest long shot, expensive and time consuming)
3- Buy a donor vehicle: eg bronco, blazer, s10, ranger. and bodyswap (still a bit out there, but can be done)
edit: i just remembered you said you wanted to stay original when it comes to the frame, so my post is for the most part a waste of space. But ill see if i can fill in other stuff.
1. If it's a 4 speed manual, then why no rpm gauge?
-Kind of common. There are a good number of vehicles during and before this time with no tach. "just shift by ear" or "by feel". You could always throw on an aftermarket tach... but some look TACKY... sorry..
2. Do any of the features listed above give away it's history or modification timeline?
-Its not stock, and no... dana 44's have been around since the 50's. Datzenmike already touched on this.
3. Frame is broken on both sides as it a raises towards engine... maybe pinch weld area. Where do I begin to look for replacement frames? I know I want to stay in the same year/family. Limited welding experience. Excellent in the bolt on department.
-Even if you find a frame, it wont be "bolt on". Welding/cutting will need to be done for thetransaxle, front suspension, and maybe some body mounts... once again, the kingrat has that info.
4. Any links to threads about initial engine startup to do list prior to starting up something that has been sitting so long?
-Check/replace fluids, check spark, clean points or get new dizzy rotor and cap, fresh fuel, new filters, make sure the webers bowls are filled/primed, check battery voltage. Could go futher like devarnishing the fuel tank ect... but its up to you how in depth you go,
5. Any links to threads about initial turn over of carburetor, radiator, electrical, transmission prior to first start?
-Huh? like... how to check to see if these work or in serviceable shape?
ah well shit,looks like 90% of my post is just wasted space.