The B16 will handle more power, but if your only going for 350hp an LS will work fine. If your tune is real good you could do it on stock pistons, but it would be a timebomb. I’d get forged pistons, ARP rod bolts and get it balanced. Just punch out the block enough to make sure the cyls are straight. Use a good oil pump and keep the rpm’s down(below 8k). BTW, a GT35 is a pretty big turbo for 350hp. You could downsize and pick up a lot of midrange power + save money