best diecast brand and place to buy?

Are you looking for Mopars only?

Here's a 1970 Hemi 'Cuda

1970 Chevelle SS 454

1970 Boss 429 Mustang

1964 GTO

Shelby Cobra 427 SC

1957 Chevy Belair

I've got a bunch of Petty cars from this place, they're really nice. Here's a few that I found:

I don't have this one, I'm gonna pick it up: 200th Win Grand Prix

Richard Petty Tractor Trailer