want to change from manual steering to power. I have the box, but it looks like the shaft for the pitman arm is much larger than the manual. Also on the P/S unit, the joint(where it hooks to center link) is attached to the pitman arm.
What pitman arm do I need to solve this?

if I recall correctly, you are going to need a P/S pitman arm for the gearbox. http://www.ecklerschevelle.com/product.asp?pf_id=608418&dept_id=1840&cm_mmc=Froogle-_-Suspension%2C+Chassis+%26+Steering+-+Steering+-+Other-_-608418-_-X# (http://www.ecklerschevelle.com/product.asp?pf_id=608418&dept_id=1840&cm_mmc=Froogle-_-Suspension%2C+Chassis+%26+Steering+-+Steering+-+Other-_-608418-_-X#)

http://www.ecklerschevelle.com/images/chevelle/large/l_608418.jpg

I'm not sure if the steering joint for the linkage is larger.

Thanks, Greg