first of all, if you want to use the b17 crank on the b18 block, just stick w/ the b17 block. essentially, using the b17 crank will decrease the displacement, which is the whole point of doing the ls/vtec.
imo, rod/stroke is way over weighed, although the r/s is not optimal, the motor will still run great for extended periods of time if built right. if you just slap a stock ls block on and rev it to 8500 rpm of course you are going to detonate it. you will at least need a block girdle, balancing, and good fuel tuning.
i'll look for the link i had about ls/vtec and put it up once i find it.
here's a decent how to--
http://www.c-speedracing.com/howto/lsvtec/lsvtec.php