Personally i'd swap the 53 and 54 back over and do something like this
51 Newcastle- Northumberland Park
53 Cramlingon- Whitley Bay (old 343)
54 Newcastle- North Shields (old 356)
56 Newcastle- Whitley Bay ( old 355)
57/57A both go to North Shields
57 via Preston Grange Morrisons and Preston Road North 57A unchanged