Some Merlin 30 series were single speed, and some 2 speed.
30 was single speed
31 2 speed
32 single speed
33 2 speed
34 2 speed
35 single speed
38 2 speed (Packard built Merlin 22)
Lumsden has the following 40 50 series engines
45
45M (cropped supercharger)
46
47
50
50A
50M (cropped supercharger)
55
55A
55M (cropped supercharger)
55MA (cropped supercharger, 2 piece blocks)
56
All engines 60 and above were two stage units.