Well, before you put it in there,you may want to consider the cam and the pistons. As I recall, the older cad's had 427 engines in them. That's a LOT of power because the Cad's hauled around a LOT of steel and extras. I still have access to a good '73 and it always surprises me how dam fast that stock car goes (and quietly)
You may want to re-think the 350 if my recollection is correct. Adding the extras may give you the power but future repairs may make the it more reasonable to go the extra cost up front for the bigger block.