Buyig a 4spd trans

It would depend on the bell housing and flywheel combo you get. But I think about the biggest you can go is a 10 1/2. As to what clutch it wil depend on what spline you trans is. I have a 10 1/2 in my 66 DArt with I believe is a 23 spline trans. Also you would want a trans for a 66 or newer as the 65 and older had a bolt on drive line at the trans.