Mk2 springs will happily fit later Mk1
Mk1 just needs to have springs with the tapering diameter at the top. Infact if it doesn't you could probably still use the Mk2 springs so long as you swap the top spring caps over too.
My Mk1 Cab runs Mk28V front springs with half a coil cut off to stop it sitting too high. The Mk2 springs are a bit stiffer and are better suited to the weight of the cab