Hang in there MrV. One thing i see is the "i gotta have that" syndrome. It gets taken apart for one thing and all of a sudden it multiplies, like with your 12-bolt, then disks, then .... so on. Usually the simplest, cheapest and most direct route is to use what GM made for the car, if for no other reason than it fits. That said, like Alky says hit you-tube you can find anything on there. Section your projects into smaller goals and if you start getting frustrated walk away and do something that makes you smile. This hobby is supposed to be fun. You will be surprised what you can do once things start coming together, and they will.
When i bought my car the wife said you hated working on cars when we could not afford the mechanic what makes this different, my response was I don't have to drive it to work tomorrow so i can walk away if i get frustrated, and thats just what i did.
I hear you. As mentioned, likely this frustration with entire project will likely pass.....until the next set back.
Currently, I am stumped on the rear end. I am converting it to disc brakes simply because when I bought the rear end, it had no brakes on it what so ever (just the drum brake backing plates). So I am only upgrading because I must. I did look on You Tube, and ironically, the inside of my differential looks different that the few I have seen on You Tube. I grant, I have a posi, but after several very close examinations, I simply can not find anything that looks like a retaining bolt, and definitely there is no bolt of any kind where the pics on You Tube show. I do not see any C clips. I see the ends of the retaining pin (or center shaft) but the center shaft goes through gears and can not be seen in the opening of the differential.
If and when I do figure out whether or not I have C clips, then figure out how to remove the axles, I have to hope/pray that nothing in the differential falls out of place. Then hope the axles themselves are okay (which by the way, I have now idea what a good or bad axle looks like). I am thinking I may be better off spending the $2K-$3K to get a full complete rear end already done. Of course, that is simply not feasible right now.
The rear end is like the engine for me. I have a full complete '67 400 engine and tranny. However, I know at the very least the engine needs new main bearings and possibly the crank to be reground. I also know the heads or pistons have not been converted to today's fuels. I do not know how to rebuild an engine. I do not know anyone that does, nor are the any reputable Pontiac engine builders in Northern California (that I am aware of). Since the entire engine (and heads) likely needs to be completely redone, I would likely be better off just dropping the $5K-$7K for a built engine from one of the online builders. But again, that concept is simply not feasible at this time.
Additionally, if I am just going to drop as much as $10K for just an engine and rear end, I might as well just drop $15K-$20K for a project already done.