Seo For Ultimate Multi Stores

I have 4 stores all with dedicated ip addresses on same server. Once complete they will be under cs cart ultimate sharing 1 back end, the store sell different items and each site name reflects what the product it sells almost exactly, Most products on each store are individual but about 10% of each are shared between stores for popular items. Also pages like contact us, about us etc are very similar in that they share the same contact numbers, store address etc.

What if any detriment will this have on seo per site, would any site suffer as Google sees them on the same sever etc. I have added /disallow to the info pages that are similar such as contact us etc but wondered what steps should I take to make them not to be seen as related.