I read some where that its bolt in but you turn the bottom hole other way. One side has more bushing then there other side on the bottom coil. Put the least amount of bushing near the spindle. Hope that makes sense. I’ll find the post.
s13 and s14 have different rear mounts. So your s13 coils will not mount to a s14 rear spindle. However, and s13 and s14 rear spindle are exactly the same minus the way the shock mounts to the spindle. So you can just use a s13 spindle on your s14 subframe, with all the s14 stuff.
Even if you do somehow get your coilover on it, you won’t be able to engage enough threads. So with safety in mind, and the fact that s13 spindles can be hand for like $5. Swap over to s13 spindles, using your s14 5 lug or watever, because its all interchangeable.
I did the subframe swap last year… You can use all s14 parts including spindle. If you use the s14 bolts for the rear spindles there would be enough threads.
You used the SPL Conversion bushings as well, I’m assuming? How much did you shim it? I know you have the option of raising the subframe from 1/4" to 1/2" with the SPL Conversion bushings.