Most small blocks respond better with a lower first gear. (M20) Especially a Z/28. They have no torque. I have the original M21 in my Z. Fortunally it has 4:10's or it would have a hard time just pulling out. I have a fresh M20 ready for it, just to lazy to change it. BB's have more torque so the M21 is a little better in mid range I believe. I think you could probably get what you wanted back then.
