Early struts will have a spanner type where the strut rod enters the housing so you can replace the strut inserts. Late struts are sealed, but can be "converted" to use Koni adjustable inserts.
Early rear swing arms are steel, late swing arms are aluminum. Early and late cars use different rear shocks.
For more info go here:
http://www.*****************.com/Porsche_924_944_968_s/20.htm
Or, you can send them an e-mail:
sales@*****************.com
These guys know 944 suspension and will steer you in the right direction.