No cons really besides traction. One of my mates done this conversion along with basic supporting mods and we were blown away with the results. Although he wasn't pushing massive power (208rwks), the response of the rb25 along with the weight of the 32 made it a bit of a street weapon. Here's the link of his for sale ad.
http://www.skylinesaustralia.com/forums/SOLD-t130416.html