G87.20 in 986 Boxster S
 

How difficult is to replace Getrag G86.20 in 986 Boxster S with newer G87.20 unit? Apparently shifting cables need to be different and muffler bracket needs some work. Is it enough clearance on top? Will I need new slave cylinder piping? New axles? New transmission mounts?

The bellhousing is different so half the bolts don't line up and the starter motor is in the wrong position. The driveshafts are unequal length so you need the 987 shafts but they don't have the correct ends for the 986 hubs. You can swap them over but it's not simple, they are a press fit and not designed to be serviceable, I did it and had to tack weld mine back together. The shifter cables are different so you'll need these also. The slave cylinder is the same so will just swap over. I don't know about the clearance, the 987 box has the bracket for the shifter cables on the top so possibly not.

Then I wonder how people put 987 engine into 986 car ...
Porsche Boxster Engine Conversion Project - 986 / 987 (1997-08) - Pelican Parts Technical Article
if bell housing is different.
http://i.ebayimg.com/images/g/-7EAAOSw3ydVnVHZ/s-l1600.jpg
starter motor seems to be at the same location is mine. I guess I miss something.

http://i62.tinypic.com/2r77xb5.jpg

This is a G86.20 transaxle with an Audi S4 2.7 spacer plate on. The spacer plate is a perfect match for the G87.20 transaxle.

Imput shaft splines are different so you need a 987 clutch disc. Yes Pelican 101 projects book is wrong.