there is a tool called a ridge reamer for such a problem
personaly almost all engines i have had appart have this unworn band. while i was at collage i did a bit of casual work in a engine rebuilders/machine shop
the old boy that ran the show would just run his fingernail up and down it if it hooked up on the ridge it got reamed off and if it slid over it it was fine.
been as the new ring is traveling exactly to the same point and zetec top rings have a chanferd top and bottom corners you should be ok
you could just put it all back together as is with some new gaskets get yor car through iva then bung in a brand new one then it would be a bolt in job or you thort about a service exchange(recon) short or long engine that would be another option
my engine cot me 50quid with loads of odds and ends i looked at it as what have i got to louse at least i could flog off some of the bits and get my money back. new zetecs are cheap but all the extra hassle of fitting an old cvh then converting it over after or new and extra emmisions for iva and all the cars life was not worth it for me.
i have rebilt mine for much less than a recon, used low milage(usualy of unkown helth) or a new one so im happy. i have uprated the big end bolts, fitted under piston oil jets and shortened the sump while i had it appart
you still have plenty of options dont worry about it
