The 93's E7TE heads are better than the 71 small block heads. Should be close to the same size combustion chambers too. If you're going to do it, then at least port the exhaust sides of the E7's. opening up the roof and walls to match the gasket, then blend this down into the bowls under the valves. On the intake sides, just a bowl cleanup and gasket match are all thats needed. As for pushrod length change, I'm not real sure you'll need that. A set of pedestal mount full roller 1.7 rockers would compliment the swap as well.