I have a set of stock cast iron manifolds going back on my 60 Starliner replacing the Red's headers. As the headers used the small head bolts, what can I use to install the stock manifolds? I read on here that they are 3/8 NC threads about 1-1/4" long. Is this correct? What grade should I use if I go to the hardware store? Flat washers or no washers? Also, what about the two studs connecting to the tailpipes as I want to replace those as well. No heat risers installed. Thanks