I think it'll fit fine. Haven't done it, but we use a 328i driveshaft on our swaps (with a zf), so makes sense that a 318i or 325i driveshaft will fit with Getrag. They can compact and lengthen some.
I found this. Guy said he had the two next to each other and couldn't tell the difference.
https://www.bimmerforums.com/forum/s...-into-98-318ti Go for it. Manual swap is worth it. Remember to jumper the auto selector park bit. The rest is straight forward.