My '62 shop manual says to tighten the center bolts 25-30 foot pounds
and the outer bolts 15-20 foot pounds. I don't see any mention of a
sequence but I'd say do it from the center out.
Be careful with the bolts all the way at the end of the exhaust manifold. If you have them there. I over tightened mine and cracked the ear off the end of the manifold, I have seen photos where some engines only have a pin there and no bolt so I was lucky because the next bolt inward holds the exhaust tight enough so the cracked ear doesn't seem to affect it as there is no leakage.
