If this is going to be your first build, or you're on any kind of a budget; walk away. Good parts aren't cheap (even compared to what we're used to with Mopars), and parts availability is worse (especially for Red Ram and DeSoto hemis) than what we're dealing with on LA and B motors. And as said; fitment into '60s-'70s A bodies can be a challenge, especially for a novice.
Early Hemis are sweet, but honestly you'd basically build one as eye candy; and nothing wrong with that- but for $$ spent you'll go a lot further with an LA/B motor.
Had a DeSoto Fire Dome in a '67 Dart back in the day, and parts availability sucked even then.