For the power steering, unless you pan of an IFS swap, rack and pinion is pretty much out. Those do not work very well with an I beam axle, partly due to the mickey mouse steering shaft setup required, but also due to the excessive amount to extra weight added to the axle itself. There are other ways of getting power steering, mostly using either a Saginaw or Toyota steering box. The former will be much easier to acquire, the latter fits better.
The 700R4 will require an adapter plate for the 261, either Langdon's or Buffalo will have the kits required.
As far as getting parts from the salvage yards, it depends on what parts you're after as to whether you're really saving anything. You have to pretty much assume anything from a salvage yeard will require refurbishing, so you need to take that into account. Things like transmissions, rear ends, engines, and perhaps any non-wear items will be fine from the salvage yard. But some items, like steering gear and brake compnents, either require special equipment to refurbish, or are simply more cost effective to get new/reman from the parts store, with perhaps salvage yard parts only being good for a core. Some parts, such as tie rods and brake rotors/drums, new is the only way to go, as they are generally non-serviceable, and not worth messing with, as they can be purchased new for very reasonable prices.
Now, if you're needing to know what parts are used on other vehicles, most salvage yards will have a Hollander manual, which has all the interchange information. The Hollander manuals are also available to the general public, but are somewhat spendy.
