I respectfully disagree on both of those points...
1.) Yes, McMaster carries alot of stuff, but doesn't carry everything. And alot of the fasteners in a vehicle are specials. And as a further example, the company I work for sells parts through them (disc springs), but they've only got a portion of the product offerings we have.
2.) Their website search engine is one of the best, compared to their competitors. Using Grainger or MSC's websites to find specific items is usually much more challenging (although they are getting better).
And don't get me wrong, I love McMaster, they're are an exceptional catalog house, and an excellent resource. And I order from them at least 3 times a week on average, and sometimes every day. Next day delivery of most anything in the catalog is pretty impressive, too. Just trying to say that even McMaster Carr, as awesome as they are, has its limits.
To the OP, glad to hear you found the parts you needed.
'JustDreamin'