Here are two quilt tops I rescued for $1 The butterfly one has some rips in it at the bottom row. Should I just take the row off or try to mend it? The other top has lost many of its pieces of fabric. Would it be worth the effort to find 30's fabrics and fix that one too or scrap the idea? And would I need to do it all by hand since the original makers did?

For the butterfly one...I would just cut off the bottom row. For the other one.. I am not sure if I personally would take the time to replace the peices, but you can that surely is an option.

It depends on what you want to do with them if repaired and finished and how much time you want to put into it.
You might consider taking them apart and saving and using the good squares and discarding the bad ones. You can certainly find repro fabrics but I woud suggest fading the fabric to look like that in the qults or you might find something at the Thrift store in clothing that could be used.
But as I said above - depends on use and time.

I have an old rescued top too because I was going to replace the bad pieces. Now I think I will just cut a piece out and hang it up in a frame. The difference in the new fabric (color and feel) is too much.

You should be OK cutting off the ripped row though and use that top.

Since I am a lover of old quilts I would do everything possible to restore them. In the past I have gone as far as taking an old quilt apart that was really wonky and squaring the blocks and putting them back together with 30's sashing and borders. I actually find more satisfaction in restoring the old than making new.

Because the tears on the butterflies are so bad I think the only choice is to remove that row. I would definitely replace fabrics on the flowers. It is not that hard to find fabrics that will blend in. Use soft colors and use shades and tints that were used then.