76 4 speed OD

I've got a 76 dart with a cast iron case 4 speed OD. are these rare or are the aluminum ones rare, or neither. I thought I read somewhere the cast iron ones are rare thanks
Rare? Guess it depends on how you look at it.cast iron ones are more rigid/stronger so they are more desirable.I don't know the production numbers on them but I have seen quite a few of them.