Can I use 1000v rectifier diodes instead of 600v rectifier diodes?
In general, it is safe to be overly conservative with a component specification. If your design calls for 600V rated diodes, then using diodes rated for 1000V shouldn't hurt anything, all else begin equal.

However, you have only provided information for the voltage rating. If the 1000V diodes can't handle 1A of current, or are insufficient in some other area, you could still have issues.