If a writer is writing fiction, why does it have to be accurate at all? I don't get that. Doesn't fiction mean something feigned, invented or imagined? For instance, I've written a story that takes place during prohibition, but I have a lot of people drinking: a) because when it comes to booze no self-respecting American is going to let something like the law get in the way and b) because I do believe a lot of people actually did continue to brew and drink during the entire period between 1920 and 1933 and c) I love anachronisms! So, if I have people drinking beer and having radios in their cars before car-radios were installed will that be a problem?
First of all, drinking during prohibition isn't an anachronism; not drinking during prohibition is. Most drinking took place in homes and back rooms and private clubs. Restaurants didn't allow open drinking in the main dining room for fear of losing their liquor licenses.
Now, if Calvin Coolidge walks into a Chicago restaurant during prohibition and everyone in the place is drinking--and talking on a cell phone--you're either writing alternate history or you're writing a script for a Mel Brooks movie or you've screwed up.
For some reason readers will devour a story set in the 19th-century about a count who's been alive hundreds of years and drinks blood and can turn into a bat. But throw in a scene in which the count is wearing an iPod, and those same readers will toss the book against the wall. Maybe readers want to believe published authors are smarter than they are, and when the author puts a radio in a car before either was invented, the reader loses respect for the author.
As a lover of anachronisms, you should try writing alternate history, where the anachronisms are intentional and expected. Just ask yourself, How would the world have been different in 1905 if there had been radios in cars? The book will practically write itself.