Yes, MT's are STC'd for the full 337 line, here is a link to the STC:
http://rgl.faa.gov/Regulatory_and_Gu...2?OpenDocument
Application Date:
12/01/1999
Status:
Amended, 05/16/2006
Responsible Office:
ACE-115A Atlanta Aircraft Certification Office Tel: (404) 474-5500
TC Number -- Make -- Model:
A2CE -- Cessna Aircraft Company, The -- 336
A6CE -- Cessna Aircraft Company, The -- 337
A6CE -- Cessna Aircraft Company, The -- 337A
A6CE -- Cessna Aircraft Company, The -- 337B
A6CE -- Cessna Aircraft Company, The -- 337C
A6CE -- Cessna Aircraft Company, The -- 337D
A6CE -- Cessna Aircraft Company, The -- 337E
A6CE -- Cessna Aircraft Company, The -- 337F
A6CE -- Cessna Aircraft Company, The -- 337G
A6CE -- Cessna Aircraft Company, The -- 337H
A6CE -- Cessna Aircraft Company, The -- M337B
APPLICABLE MODELS: Model Number
Serial Numbers
336
633,636, 336-001 through 336-0195
337
337-0002 through 337-0239
337A (USAF 02B)
337-0240 through 337-0525 (except 337-0306 & 337-0470)
337B
337-0001, 337-0470, 337-0526 through 337-0755 (except 337-0569)
337C
337-0756 through 337-0978
337D
337-0979 through 337-1193
M337B (USAF 02A)
337-M0001 through 337-M0476
337E
33701194 through 33701316
337F
33701317 through 33701462 and 33700306 (except 33701449)
337G
33701463 through 33701815 and 33701449
337H
33701816 through 33701950 (except 33701920 and 33701923 through 33701927)