Hi "27", just a tip here, if you are going to use bolts to hold the heads in place I strongly recommend using some "special" (see photo below) very thin washers with the bolts. These washers work well with the OEM head bolts and are designed for this very purpose. If you look closely you will notice they are parallel ground AND chamfered.
These washers help keep everything nice and tight and help avoid "relaxing" the torque due to the expansion and contraction of the head material! We use them on iron heads also just as a precaution.
I would also consider machining the head bolt bosses slightly for a nicer finish, especially if the heads have been glass-beaded/shot-peened?? Just my take on it!
Thanks, Gary in N.Y.
P.S. Here's a photo of the washers, they are only .070" thick and almost entirely "invisible" on the finished product.