Magnum instead of 318?

Dropped off 65 Dart at shop yesterday to get my engine & tranny gone through. Matt calls me today & says he has a 360 magnum block from he believes the 90's that we could go through instead of 79 318 motor that's in car. He liked the thought of roller cam in magnum over old style cam & lifters. Will be upgrading to four barrel carb & intake.
Is this a good idea? Going for a mild, close to 300hp rebuild. I'm trying to keep budget low key, if I go with magnum 360 will that run more then staying with 318? I'll check back, thanks