I've been running a RedHead for 5 years now. About 1,000 miles with zero issues. It is RedHead p/n 2854 which is the Variable Ratio GM Saginaw 800 Series box. At the same time I switched from the original 17" diameter steering wheel to a 15". With the 17" wheel the "feel" is too light when combined with power assist.
I have a good core- see
http://67-72chevytrucks.com/vboard/s...=799140&page=2 , post #36. RedHead is not particular about cores, other than they need to be rebuildable. You don't have to send them EXACTLY what you are ordering. As long as it is something they can use to rebuild and re-sell. By the time you buy a core and pay for shipping it to Auburn, Washington you might as well just pay the core charge. It weighs about 30 lbs.
Of all the fixes and upgrades to my '66, the power steering was the most bang-for-the-buck.