Welcome and good luck with the conversion.
im sure soemone will come up with the parts you are after.
i can tell you few tips in regards to power steering.
i think the r33 skyline rack is tad too wide for s30 application.
another issue is that R33 and 280zx have their steering rack mounted behind the front wheels while 240z 260z 280z has in front of the front wheels.in your case this may work to your advantage if u use a LHD rear mounted rack and make it a RHD (just flipping it around and mounting it as a RHD and front mount) in theory it should work
if u mount a Rear mounted rack on the front your steering controls would be opposite. so you turn your steering to left and car turns to right. it would a very interesting and scary experience
Another issue choosing the rack is getting the dimmensions of the moving rods (lenght) as close as possible to the original rack within 10mm - 15mm max.if its slightly longer or shorter it will make the car handle very bad as the geometry will be greatly affected.
some good examples of the racks if u choosing a rhd and front mount rack is Mazda miata or MX5 or subaru liberty impreza leone etc.....
with subaru racks there is few mods and tricks to make it fit to the subframe. but apperently mazda one is pretty good with minimal mods (apperently havent done this one yet tob e 100% cetain)
there are few details and be glad to help but if u try and source a rear mount with similar dimensions and flip it. it will make your job lot easier.
if i confused lot of people ill post a picture and a diagram of the issues outlined with choosing a rack.
i found this the hard way (dont use mazda rx7 or supra rack too long)
other car that may be possible is a BMW 3 series E36 looks like it may be good fit but havent done the measurements. (for local ppl)
again i hope i havent confused the issue even more.