You can duplicate the TTT rear coilovers fairy easy.
S13 AGX rear shocks. KYB 741017 Shocks For 89-94 Nissan 240SX Rear LH or RH
Clamp On 2 Bolt Steel DOM Fabrication Clamp 1.75" Roll from eBay
Springs and threaded coil over sleeve
The only tough part is making the top hat, I turned my stock top hats down in a lathe. You could do it in a grinder.
PM me if you want more info.