Dave,
From memory, there are 2 lengths of spoke, but 4 part numbers because there are inner and outer lacing spokes of both lengths - the end result being short spokes with 80 degree head, short spokes with 100 degree head, long spokes with 80 degree head and long spokes with 100 degree head.
Hope that makes sense. Also, all your spoke lengths will be different to the Mark spokes as the Plus wheel has a 21" rim.
Regards,
Eddie.