im looking at running dual rings on my nomad, but have a few questions. i want a sram x.9 front mech  but on crc i have 4 choices, from the 4 below what would be the one i need?

SRAM X.9 9sp F-Mech Conventional BP
 
SRAM X.9 9sp F-Mech Conventional TP
 
SRAM X.9 9sp F-Mech Top Swing BP
 
SRAM X.9 9sp F-Mech Top Swing TP

also what size clame size do i need for the nomad?