As mentioned frequently on here, Ford often uses different size fittings on brake lines to prevent assembly errors.
In some cases the threaded body is different size; in others, just the 'nut-head'. There are thread adapters made for the former case, available at local parts stores like KOI and NAPA. Some reason, not Autozone! But dont worry about nuthead size if the threads fit.
EXCEPT: I recently had a problem replacing a line into a rear ABS block where the replacement fitting seemed 'loose' in the block socket. I didnt want to reflare to use the original big-head fitting so I prayed. And it sealed okay. (And yes, I checked that both it and the original fit a female coupling)
HOWEVER - if you are splicing/flaring a line anyway as I will shortly to replace rusted front-to rear lines, suggest you reuse the original nut. DONT FORGET TO COUNT FITTINGS BEFORE YOU FLARE!!! Common 'ooops!'
Another hint: Replacing a line, nut rusted solid? DONT fudge around, cut the line at the nut and use a six-point socket. Flex line nut rusted solid? same thing... not worth the hassle and odds are flex line will start leaking soon anyway.
Also, Break loose bleeders with six point socket before using box wrench during bleed. Saves your nerves.