Yes you can use a 90mm LMAF - it'll give good driveability. But, it is NOT calibrated for any injector size. Ford does this the correct way, in the EEC. You will need a tune to get it to run right though.
If they supply a fuel pump with the kit you are getting, do not use it - it's probably a Walbro pump which is a gyrator style FP intended for a return style car. It will kinda work, but driveability will be for crap and it will fail very soon. Either do an '03 Cobra tank and pumps or do a Focus pump. The Focus FP is good to about 400 RWHP usually.