I have BB Ford with Jag rear very similar to ERA.
Front: (2) QA1 Proma Star DD404 (dual adjust)
Rear: (4) QA1 Proma Star DD403 (dual adjust)
Link to expanded description:
https://www.summitracing.com/parts/qa1-dd403
Spring Rate Front: 350
Spring Rate Rear: 300
Adjustment knobs on bottom so compression/rebound
can be set for conditions on all (6) coilovers in 2 minutes.
Car tracks true and not a harsh ride at all.
Hope this helps a little.