Migration of SC File from 7.0 to 7.31

HI experts ,

we have two tracks one for webdynpro dc and another for portal components , named wdj_track and anotehr portal_track, and have software components in them as *****_Prod_WDJ_SC and ******Prod_Portal_SC respectively.

we have requirment to migrate these to 7.31 version,

i have a doubt like , we have to migrate the software components ?

or else i have to migrate each individual dc from 7.0 to 7.3 and then later  add these dcs to the DTR Track in 7.3 server.

we have a customised logon page , i.e par file please suggest a better way to migrate the same .

Regards

Govardan Raj S