"A myth about the Nissan V6 is that “its too heavy!” Lets compare some 510 vehicle weights. A stock L16, 4 speed, 2 door 510 weighs 2078lbs. A friends L20B, Z 5 speed, 2 door 510 weighs 2270 lbs. My 1970 2 door with the stock VG30 and 5 speed weighs 2210 lbs.
Michael Spreadbury"
More good reading here:
http://www.nicoclub.com/archives/installing-the-vg-30-in-a-510.html
I my setup is a bit heavier then the numbers above, but it still handles well in my opinion.