340 upgrades.

The "X" heads are natural 2.02/1.60 heads. They come off early 340 engines.
A '72 intake is a T-Q spreadbore intake and is a very good factory intake. I would go as far as a 280* cam which mostly come with a .480 lift. A Comp XE would be better being a split duration. (Helps with the exhaust which flows OK at best. With or without headers)
A aftermarket intake would be better for performance adding 10 - 15 HP, but thats your money to spend if you want the Aluminum.