Want 6.0 swap but have ???'s

ok first off I would like to know what kind of gas mileage will I get in everyday driving at a top speed of 70 mph, I commute. I bought a 6.0 lq4 all disassembled from a fellow tech for $300.00 and just want to leave the internals stock with all my existing bolt ons I have now, what can I expect? I was also wondering if 1.85 roller rockers wil make and bit of a difference with the combo I have now. I've even considered buying an ls1 and save the 6.0 to put into my Chevelle

Sounds like you want your 6.0 to have a turbo with small boost, better gas mileage and much better performance.....