are ls, b20's crank and rods length the same. see some people using b20 cranks an ls rods. or b20 block an ls internals. why is this? longer stroke?

 

the ls rods and crank are the same as the b20 the only difference between the b20 and the ls is the bore the b20 is 84 and the ls is 81.

 

LS and B20 motors use the same crank(89mm stroke) and use the rods (PR4). Only difference is the piston bore, like already mentioned. They even use the same heads except some B20's use a head with a P8R casting which has vtec sized intake valves for more flow. I believe only a few JDM B20 motors came equiped with those rare heads.
Look here to confirm LS and B20 crank and rods
www.zealautowerks.com