to be honest with you the overall rating doesn't really, matter you should be looking at their speed, CAT, CIT, SPEC. when i use the niners i usually put V. Davis as my number 1 WR.
And another thing if you audible down and get a WR a TE its a good thing because typically they are being covered by a Linebacker, which can create some favorable mismatches.
Dont worry too much about overall, just worry about how you can utilize your best players to give you the best opportunity to win.