there a quite a number of shocks available for the ty175 as which is best is a hard one to answer as people have their own preference.
i personally use be Betor 360mm between centres with 40 pound springs and im very happy with them.
others to consider are rockshocks,falcon.
whichever shock you go for get the 360mm length these give a little more travel and if you put the top of the forks level with the top yoke you get a little more ground clearance. hope this helps Alan