you beefed up the rods? I would take it to 8500 (once that oil problem gets fixed) The weak parts of the LS bottom end are (in this order, and imo) The rod bolts, lack of a girdle, rods (any weakness compared to GsR rods is due to weaker rod bolts). If I had upgraded rods (with ARP rod bolts 9/10 times they come I think) I'd take it to 8500 with minimal worries, add a girdle and you should hear songs playing cause you're bottom end will sing as high as you want it.

PS Boost is for sissies (hehe)