You'd need to select a single object type, not two separate varchar2
values. Something like
EXECUTE IMMEDIATE
'SELECT ItemRec( ''ABCD'', ''CUSTID:'' ) FROM dual'
BULK COLLECT INTO v_items;
In your code sample, there would be no reason to use dynamic SQL here, it's only complicating the code. Hopefully, there is an actual reason to use dynamic SQL in the actual code that you're building.