Yes you can,As long as the bolt holes are drilled for the 3/8 ,some blocks have the bosses there but are not drilled.It don't matter if its a 265,283,327,350 or a 400 small block,they all had the bosses there to do the front mounts. As far as the manifolds go, If they fit and your happy with them and they don't come in contact with anything then use them,Be sure to see where your exhaust pipe will go when use the ones you choose. And one more thing to think about is don't use too long of a bolt in the hole that goes through to the fuel pump rod, if you put too long in there it will bind up the fuel pump rod and your fuel pump will not work.
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