Your front spring rate will dictate the use or not of coilovers out back.
On my street driven '86 I'm using 250lb front springs so I had no option but to use conventional springs with the T/A.
Wouldn't 350lb front springs be the minimum in order to run coilovers out back to get the proper balance front to rear(250lb rears)?
I had 300lb springs up front for one summer and the ride on the roads up here was a killer,went back to the 250's.I give you guys credit when running high spring rates on the street,in my younger years I would have done it but not any more.lol
2 owner '86 Med.Canyon Red Met.(original paint) T-top,5 speed,3.55 rear,MAF conversion(A9L).MM adj. RLCAs,T/A and Panhard Bar,spring rate:375#-440#,MM C/C plates,STB,4pt KMB,FLSFC's,'03 Cobra rack-n-pinion w/ Saginaw pump conversion.Bilstein MM coilover conversion and A-arms,spring rate:250#.