will the mags and tires from a 98 civic work on my fit if they are sized 205 45 16 ?

 

depends what offset the wheels are....
if they are over +45 offset and you're not lowered you should be perfectly fine with those size tires.

if you're lowered and below +45 offset you will probably need to play with camber and fender rolling to avoid problems.

-Ricky