Hi & welcome to the forum,
I can't answer the spring length question. If the two springs appear to be matched & their lengths ars nearly the same, they are probably ok. As you know, the red stripe springs were the latest version of their front springs.
The shock modification is because Moss sends out rebuilt shocks that have MG shock bodies.
I would seriously consider returning them to Moss & having your old shocks rebuilt by Peter at:
https://www.nosimport.com/shoxcatalog.htm
They do a better than new rebuild at very reasonable cost & their work carries a very long guarantee.
If you are concerned about the springs, it would certainly be better to use the correct shocks also. If you no longer have your original shocks, consider finding correct used shocks that are suitable for rebuilding.
Best of luck,
D