when comparing the whole strut assembly to a e12 they are very similar.
differences are:
E12 540mm long / E28 560 mm long
E12 coils are 8- 110mm x 12mm dia, E28 9- 90 mm x 11mm dia
E12 bottom attachem is to a U channel
E28 attachment is a bolt side bolt only bolt size is the same.
So I am considering swapping the bottom mount rubber and sleeve on the E28 strut and seeing how it fits in my E12.
new rear Billys are $580 each here , New at US prices of $100 each plus delivery say $90 US.
See how I go.
heres some pics for comparison
(sorry about the size - )
e12, e28 then bilstein
[tops appear identical bolts are the same

bottom has same dia rubber bushing but different steel ring, maybe cut off or swap over?


chow