Well it looks like the 2 sizes will not match up very well. The 800 x 600 swfs have a 4:3 aspect ratio. Since that ratio will have to be maintained in order to maintain the correct shape of things, the widest those swfs will display would be 1024 X 768. In this case the constraining issue is the height, not the width. So they would display with 100+ pixels of blank space on either side.
To resize I suppose you could create a new doc in Flash (1024 x 768), import the swf to library, place onto the stage and resize down in the properties panel. Keep in mind that any bitmaps included may pixilate and/or there may be other issues. Depending on content, you could play with greater width and see what is acceptable as far as distortion goes.
Good luck,
EfV