Exhaust Manifold Bolts and Gaskets - Sources?

Took the exhaust manifold off, and would love to change the bolts; the threaded shafts are skinny, so would love to avoid breaking in the head in the future. Any sources for these bolts? Specs of the bolts?

Also, the OEM exhaust manifold gaskets seem to have spark plug heat shields attached. Are these still available, or should I reuse the OEMs? They seem to be in good condition, but would love to replace with new, of equal quality, if I can.

Car is a 1965 Dart, 273 V8. Thanks.