There could be a crossover somewhere in the system and you won't get full range out of your new speaker. I buy from Crutchfield because they know exactly what goes in each spot and will include any adapters needed for your vehicle.
I'm no Toyota expert but the front crossmember/spring hanger is what you see on the SAS Toyotas. Probably means the frame is newer than 1985. If you're happy with the height just use those springs.
So in the rear the uppers are now 2" shorter than lowers? What is the difference in the front? What are your anti squat/anti dive numbers if you don't mind? I'm working on my first f/r 4 link and I'm curious what works good in our area.
If you plan to offroad this at all that 1st gear would suck. My T18 with 3.09 second gear is not always enough. If you plan to race it then it should be great.