408 Magnum New Build, Gutless of idle

I thought there were aftermarket Mopar Performance heads called “RT” that were magnum based of course

don’t fuel injection systems like wider center lines?

the stock stamped rockers will make that cam a little smaller since they are actually 1.46:1 (not 100% number for magnum rockers)

Yes, you are correct regards those heads
Great heads that make excellent power.
I went mid 11’s with them on a stock stroke 318( magazine enginemasters motor) with a downsized cam, and 10.44 compression at 3400 pounds