ok ive been searching and reading about trannies but im still confused.
This is gunna seem like a nutty question but oh well. Will a USDM civic tranny fit in my 91 integra without haveing to change to a different clutch or driveshafts.
no.
i assume you mean 99-00 civic SI b16 tranny.
if so, you would need to convert to hydro tranny using the hasport kit or Zoom method and get a 92+ b series clutch