Help with trainig for OO 2012, gearing set up for ss roadie

Looking at completing a virgin attempt at Otway Odessey 100 next year on my ss mtb however I need to rack up some roadie km’s in the same vein doing some serious climbing here in Melbz north east (Kinglake, Flowerdale, Kew Bouli etc) as time does not always permit to get out on the mtb.

I have an old Langster that Im going to train on but change it over to a SS to replicate the training effort and wonder what gearing peeps can recommend for general hill climbing etc.

Currently has a miche 48T up front and various 14, 16 and 18t fixed rear so I need to get a _____ tooth SS rear to suit.

Any ideas or help from experience would be appreciated?
Thanks