Front shocks for all X19's are the same, early units are able to be refurbished with an insert as they are dismountable, later types (and most aftermarket units of early and late types) are sealed units not designed to be refurbished / reconditioned.
Rear shocks are different.
There are two major differences from early (four speed type) to late (five speed type).
The first is to do with the configuration of the shock shaft. Early units use an alloy cone (the same as used at the front) at the top of the shock (under the rubber isolation mount) whereas the later units this cone assembly is integral with the top spring seat/bump stop assembly. This means the early shocks have a stepped thicker section at the top of the shaft, Later type struts have a thinner seation below the thread (but you can use these with an additional sleeve to replicate the step)
The second difference is the style of lower mounting point.
Early and late types are different as the rear CV joints are different for four and five speed models. Early type struts will foul the later large CV joints. Late struts can be fitted to four speed cars.
There are also two distinctly different five speed rear strut assemblies. One has a higher positioned lower spring seat, which will make the rear of the car sit higher.
I've been a Fiat parts reseller for over 25 years, and can verify this information with the OEM Way-Assuto parts catalogue. I can also post some pics of the differences if you need more clarification.
SteveC
