Upgrade exam for SCBCD 5 for any previous version of SCBCD is available and it is CX-310-092.
For Syllabus comparison and topics visit this sun link http://www.sun.com/training/catalog/courses/CX-310-092.xml You will get all the details required for the certification regarding syllabus and topics.
iam not sure about the difference in exam questions because iam also preparing for 310-091 now.
Hope this information helps you.
THANKS IN ADVANCE,
SCBCD in progress