I'm not sure I'd spend $800 for those parts. Unless the car has more than a rear axle and power steering for your project you might be able to spend your money better somewhere else.
Around here $100 to $150 will buy most any rear-end at a wrecking yard, and that should be enough to buy the complete IFS with power steering from one of the more common subframe donors.
I have the rear from under a '73 Chevelle under my 55 1st, and it fits real nice. I paid less than $100 for the complete car with a 350 and turbo 350.
The kits that put power steering on the original straight axle use the power steering box off a of 73-87 Chev pickup, not the one off a car like the Caprice.
I'd encourage you to look elsewhere unless this car has lots of parts you're willing to work hard to adapt.
