[71tahoe]

Everything will bolt up to the stock manual 3 speed in the stock location but you will have some potential clearance issues with some tall valve covers and clutch linkage issues with headers and newer block.

The z-bar can be bent around the headers and a bracket can be made for the pivot near the oil filter if needed.

If you are talking about the governor springs on the automatic, they are easy to get to and should be easy to change. If it's internal, I really don't have any idea how hard. You should change your radiator to a 3 or 4 core either way you go but get one with a transmission cooler for the auto. You will have to extend stock cooler lines about 4" or fab your own. Adding an auto also means a new starter that attaches to the block and not the bellhousing.

EDIT: forgot to mention that for the auto you will need to cut the existing transmission crossmember and get one for an auto.