For the rear id go for a custom set of springs so you can choose how stiff you want it to be and the height, And some decent shockies.
If you go S13 you will most likely need to use s13 lower control arms as well, You will need to get a tape measure out and measure up RT142 corona lower control arms and s13 ones. I don't even know if the top of the strut bolts in.
A coil over kit with sleeves you can weld on might be a better option.
Your diff is a F series 7.5 inch if i remember correctly, And a LSD from a MA61 supra do fit it, TT142 LSD centers fit as well but are relatively rare.