HELP: manifold bolt sizes

I am trying to figure out what size manifold bolts to get for my 66 Mustang with a 302 and 1985, YES, 1985 5.0 heads. I am using 289 HIPO cast iron manifolds. I assume that I need one half longer than the other half. Can anyone tell me the thread size and length, assuming they can be purchased at the hardware store OR where I can order a set of bolts.
I am pretty sure the threads are different than those that were used on the 1966 heads with manifolds. (metric vs SAE)

thanks
Jimmy Bost