I've been playing on chess.com standard time (not blitz) for a while with a rating of around 1670, but my FIDE rating is still around 1600, still growing. Is there an actual conversion available for these ratings?
I play blitz there every day for many hours. My rating periodically oscillates between 1850 and 2050, which is a span of 200 points. This has little to do with my varying strength because it depends mostly on which opponents I happen to run into. This phenomenon puts a certain constraint on your idea of a conversion table.
I added two more comments to this answer. See below.
There isn't, but I believe the general consensus on this question on chess.com's forums is that your actual ELO/FIDE rating should be lower than your chess.com rating after you get a decent amount of games on both.
I'm not really sure how much lower it should be though. Perhaps the forums on Chess.com hold the answer.