Will an 8 1/4" bolt right in to my 7 1/4" spot?

I have a 68 Valiant with a slant six auto 7 1/4". I want to convert to BBP and discs upfront. I have a buddy that has a BBP 8 1/4" out of a dart he thinks. Will my current driveshaft work with this? The rearend is complete with E brake cables as well. Will these cables work with my setup or my current ones work with it? thanks!