Stuart,
I have attached a gearbox ratio calulator. It takes into account Diff, Tyre, Rim and gives you revs at different speeds on various Gearboxes.
Also check these websites for more Tremec info
http://www.moderndriveline.com/Techn...its/tremec.htm
http://www.malwoodauto.com.au/
and CAPA Performance in SA had Tremecs at a great price a few months ago.
http://www.capa.com.au/eaton.htm
Cheers
TC