1. the ls crank is only a slightly bigger stroke than stock b18c. 89mm vs. 87.2mm
2. definitely possible but dependant on how big a stroke. you'd need a 95mm+

it really depends on how much power you want to make and how much money you want to spend. a big crank calls for custom rods and pistons and clearancing the block. which is not cheap.

if this is your daily driver, imo go no bigger than a 92mm stroke, especially if you intend to hit a road course. the bigger you go the more abuse your bearings take and you cant rev as high.

i was contemplating going with an 85x98 b18c1 setup myself, but for a daily driver it's probably going to be too much. so i scaled it back to 85x89, but havent ruled out a 92 or 95 crank.