Rear Coilovers:Need skinny 2.5" O.D..

[Whit]

Want to convert my 73 rona mk2 mx23 to rear coilovers and eliminate the stock coil springs.
So I can then replace the lower arms that the stock coils mount on and replace with Adjustable T3 link bar.

There is limited space in the upper shock mount area.So 2.5 inch O.D. wouild be the size needed.
Hard time find a brand, i remembering seeing billstein coilovers a while back??