Winstrol will help in the muscle preservation process, mainly in keeping down the rate of catabolism to a certain extent while in Ketosis - catabolism being the base of the diet that is.
I would actually suggest doing 300-400mg Test Prop w/ 50mg Winny ED. and .25mg armidex ED (depending on your estrogenic response to test). It's not much, but to most uses this will yield a high anabolic environment in a highly catabolic state - Ketosis.
Mr.X