Part Numbering

HELP!!! We were using a 3 letter customer prefix and the customers
number from their print. 2 years ago we change our system to a 3
letter customer prefix then assigning our own 6 digit number. When
the order goes on we currently enter our 6 digit part number w/out
the customer prefix. This is creating Havoc on our customer cross
reference and order entry. I have advised that we assign the prefix
at the time the order is entered. We use a 3 letter prefix to
identify which customer the part is for.

I would like to know the following:
1. How others number their part numbers.
2. What is the easiest way to clean up our CUSTXNum table
3. Does anyone have suggestions on a part numbering system that will
identify the customer in part maintenance/tracker and on the job
routers and keep our cross reference table easy to use.