Will a solid driveshaft out of a 98 forester work in my 2003 Impreza rs? Or Willa 02-07 wrx work?

As long as they're the same transmission. Like both auto or both manual. That dictates the length of the driveshaft.

Will a solid driveshaft out of a 98 forester work in my 2003 Impreza rs? Or Willa 02-07 wrx work?

 

Neither of those have "solid" driveshafts.

 

Both are hollow 2 piece designs. (carrier bearing in middle)

Companies make one piece driveshafts - look up what years/models they fit and see if it includes the ones you’re asking about.

 

If you did mean a “1998 one piece forester” driveshaft I think Phase II transmissions have different length transmissions and driveshafts.

Companies make one piece driveshafts - look up what years/models they fit and see if it includes the ones you’re asking about.

If you did mean a “1998 one piece forester” driveshaft I think Phase II transmissions have different length transmissions and driveshafts.

nope, as long as they're both auto or both manual, they're the same length.

nope, as long as they're both auto or both manual, they're the same length.

copy thanks - other than auto/manual what other transmission length difference exists...i feel like there's another difference.  maybe it's just EA/EJ swaps?

Different model year ranges have different lengths. And different models as well. Legacy is different length than impreza and forester.