heres another link for the ls/vtec conversion
http://www.g2ic.com/tegtips/engine/6.html
yea the LS pistons redline at 6500 (or ~6700 with the 92-93) so rebuild it if u want it reliable past that so u can make full use of the VTEC. and this conversion costs ~2k! so make sure it is even legal to do (smog wise) good luck. u may want to look into just buying a b18c1 or boosting ur b18a1...