DIY coil-over help

[autox320]

It's been a few years since I made GC's for my E21 so take it easy on me. I've searched and can't find the exact answers so making this thread.

Car will be track oriented E30 318is. Browsed over the various diy threads on koni's.

Whats the difference between these two shorter koni's 8641-1144 vs 8641-1198 as far as fitment in a shortened strut tube? I plan to cut out 2 inches from the tubes. Are the diameters different? Length?

What's the difference between Ground Control's two conversion kits?
one says specifically for the 325ix

http://www.ground-control-store.com/products/description.php/II=902/CA=241

and the standard e30 kit looks the same but different sku number

http://www.ground-controlstore.com/products/description.php/II=121/CA=241

Planning to use Koni 8041-1186SPT for the rears based on various threads these are top adjustable making more sense.
Looking at spring rates
450 lbs/in front (factory front sway)
650 lbs/in rear (no rear bar)

Any other suggestions?

Thanks!

[Northern]

Well the ix has a different strut housing and strut mount, so there may be some differences in the upper perch or spring length.

If you're looking at those spring rates, you should definitely look into the ge coilover kits. The group buy kits from last year come up for cheap pretty often and are good quality setups.