If you do a definition only export (rows=n) on the 7.2 database, and then use Import to generate a datafile of the create statements, you will then get the necessary create statements in an editable format.
Since tablespace size is determined by the number and size of it's data files, there are several other factors that need to be considered. Such as does your OS have a file size limit(For determining the number of files needed)? Is the OS 32 bit or 64bit (also a limiter of file size).
You can try
select tablespace_name,sum(bytes)/(1048576)
from dba_extents;
to see how big your tablespaces need to be.
Joseph R.P. Maloney, CSP,CDP,CCP
'The answer is 42'