New heads/intake/rear end

Cast iron for me, they hold the seal longer, less likely to crack, less chances of pulling the spark plug threads out. Holds the heat better.

Aluminum is easier to port so per shop hour its cheaper but cheaper is not always the best.

Both type of heads are good but seems like those factory motor heads are always leaking after 10 years or so.

We should be happy Mopar did not use aluminum heads back in the 60's and 70's, otherwise 80% of them would be junk today.