migrating 1.x urls to 2.x ?

I have a large 1.x Gallery with >20Gb of photos, I have migrated this to Gallery 2.x and all is well, however I now find an issue whereby there are a lot of forums posts on my site that point to old gallery1.x album / photos and if i simply bin the old gallery and its data then all these images will suddenly be missing in the forums.

I was thinking that others must have encountered similar issues before and might have a solution ?

The only two ways I can see to tackle the problem are mod rewrites or a search and replace somehow of the MySQL forum entries for urls ??????