65 Cuda wheels..which way to go?

Johnny Dart said
I stayed a little smaller on the tires on this car,because I didnt want to rob power from the /6.

Might change my mind with this new motor though. This thing will roast these tires....

Honestly, want to go to a 15" steelie with a 60 series tire. 15's look real good these.

Does a wider tire or a taller tire rob power? I know both play a factor. But does one play a bigger factor than the other? I'm a new owner of a 1966 valiant signet. Thanks.