I use Tractor Supply. They sell nuts and bolts by the pound, you can just get a handful of what ever you need, in grade 2,5,8. They are typically cheaper than a hardware store. Though I still use a local hardware store for some specialty fasteners and metric stuff.

1947, 1950, & 1952 Chevrolet 1/2 ton
1952 GMC 450 series Cab Over Engine
1946 Chevrolet 2 Ton