Yes, you can graft over the apple. As for the zone I am guessing your talking about usda hardiness zone and not sunset zone. I can't really guide you toward a particular variety because I don't know what kind of characteristics you are looking for in an apple. You must also take into account having a suitable pollinator for your varieties. However, a resource I have found helpful in finding suitable varieties for my area and taste is kuffelcreek apple nursery, they list the 20 apple varieties that are favorited by a grower who operates in riverside california. I am sure some of the more experienced people can help you out with better info, as well as places where you can acquire scionwood.

The guy from Kuffel Creek also has some helpful videos about grafting on YouTube.

Also, if you need literature on vegetative propagation (grafting and other techniques) Google "vegetative propagation techniques" the pdf was quite useful for me.