I have experience with the Steeroids kit, in fact I bought one and still have it (it is for sale too). When I bought the kit, I had a small block in the car, and it seemed to fit really well, the only issue is selecting the correct headers. I did have to trim down one of the pieces about 1/16" on the steering column-to-rack adapter.
When I changed my car to a big block, I could not get the system to fit, specifically the headers. There may be units out there that will fit with this system, but they will be smaller tubes than the large ones I need with my 489 CI motor.
The steeroids kit is pretty simple, to be honest. One of the things that people questioned (including myself) was the strength of the outer tie rods. They look pretty thin, and in a rear steer configuration there have been questions about reliability in performance (i.e. road race) applications. To be honest though, I changed the oil in my 2002 Camaro last night, and noticed that the tie rods on this unit didn't look any thicker, albeit that this is a front steer config.
I think the answer to where the rack comes from is correct: a later model "Grand Prix" type car, not sure of the exact years, but mid to late 90's seems to ring a bell.
If anyone is interested in buying my unit, drop me an e-mail. It was used very little (one drive around the block, to be honest!). I had a buyer for it, but he flaked out on me.
69 SS, ZZ430 Look-alike, Tremec TKO, Hotchkis Suspension