The bigger ports in the EZ heads will kill off some bottom end torque but you really might not notice the difference. If you build it the same way as your 496 you'll have similar power. Maybe a little less torque and a little more hp but similar.

The Trick Flow heads will be a better choice for you but of course you'll take some financial hit selling the EZ heads. Tough choice, just depends on how flexible the budget is and what you really want to do. If you're not in a big hurry maybe put the EZ heads up for sale and see what happens. If you get good money for them then buy the TF heads. If nobody is buying EZ heads then go ahead and build with them.