It doesn't look like there is any difference. My suggestion is to call Adams and ask. I had the same question about the GT2 Undercuts vs. the GT3's and Adams' customer service was honest about there being no real difference other than the markings on the clubs. If you call please share your findings.
Adams contact information
Toll Free: (800) 709-6142
Local: (972) 673-9000
Fax: (972) 398-8818
E-mail:
info@adamsgolf.com