73-76 steering linkage in 69 barracuda..

1. Yes (although I don't have the part numbers memorized).
2. There were only two centerlinks for the wide A-body. 67-72 and 73-76. All engines in a given year range used the same link.
3. The PS box will work fine, but will likely require the use of the later link/idler/pitman due it likely being large sector. The pump will work fine if you have brackets that are compatible. I will be going through the same thing with the 440 that is going in my Barracuda as I have a '73 PS box and pump from a slant.