Source For Automotive Bolts

[CatalinaWOW]

Another source similar to other suggestions is a "pick a part" salvage yard if there are any in your area.  Those bolts are common on GM cars over a fairly long period, so take the appropriate wrenches and you should be able to collect all you need.

That's California thinking!  In many places those have all rotted to oblivion and any such bolts would be useless even if you torched them out.

Presumably they will have rotted a little slower than those exposed to the salt cycles for a similar period.

It certainly helps to live someplace where salt isn't sprayed everywhere.  When I lived in Arizona I could find suspension parts 30 years old that looked new.

OP says only some of his bolts were unusable.  Pulling appropriate parts might require either a lucky find of a summer only car, or pulling only a bolt or two from several cars.

[nctnico]

I'm trying to find some bolts for a car suspension repair and McMaster-Carr doesn't seem to have exactly what I need. Does anyone know a good place to find bolts?

Go to a car dealer for the brand or a car parts shop.

[Benta]

Just curious: why would a flanged bolt need a washer? 

Thanks for asking because I've wondered myself.

I'm guessing to reduce the force on the bolt head. The M12 bolt goes through a bracket which goes through a sleeve and the (what I call) knuckle rotates on it as the car bounces, so I imagine the constant rubbing may wear down the flange. What I also don't get is the fully threaded bolt goes through a sleeve. As the car goes up and down and the arm rotates, it will wear the threads and the threads will wear out the insert thus making it sloppy over time.

From what I'm seeing though, this isn't the case as the rust has provided a nice thick filler for any cracks. It's been so nice that I spent lots of time trying to remove these bolts; and didn't give up because they were annoying me.

The washer on the M12 is about 26mm with the bolt flange being 25mm. The washer on the M10 bolt is about 28mm with the bolt flange being 20mm.

As I've mentioned, trying to find exact parts with features that don't alter the function (i.e. a tapered head or a washer that's pressed onto the bolt threads) isn't really important. A solid bolt with a washer should do just fine.

Usually I use these moments to learn and figure out how to obtain the actual (in this case) bolts should this be a project that required precision or whatever.

Quite frankly, the more I read here, the more I'm convinced that you are trying to recreate a previous total kludge repair.
A 25 year old car would never have been built that way.

If we're talking the control arms and their mounts on the body, the tried and true way of doing this is with rubber bushings. These consist of an outer steel bushing surrounding a rubber sleeve with an inner steel bushing.
The whole thing is pressed into the control arm with a 20-ton press. The inner sleeve is bolted to the chassis bracket with a flanged (smooth!) bolt and flanged nut and tightened.
There is no mechanical movement except the twisting of the rubber sleeve when the suspension moves. This is why it's important to only tighten the bolts when the suspension is loaded, or in neutral position.

Cheers.