I won't disagree with the bulk of that except to say that the "68 - '70 body engine compartment must be bigger, 'cause I haven't had any space issues. And yes, you must have really bad luck because Mopar wedges certainly aren't known for being high maintenance engines.
A 451 low deck stroker (or similar) is a great engine; a buddy has one in his '68 Charger with a 6 pack setup on it and it runs great. The only downside is equivalent performance to a 440 with increased build cost but if I had an original 383 car, that's the way I would go too.
Dave