Dads Barracuda

So here is where I ask for help on my build. It presently has a 318 2bbl, 904 trans and 7 1/4 rear. I got a 360 la with roller cam, got a 625 demon, airgap intake and 340/360 exhaust, and 3.55 posi rear. The 308 heads are at the shop and I'm wondering how far to take them. Planning on port matching and some bowl work. What advantage is there in double groove valves vs single? Head shop said he could mill the heads 30 without different pushrods. Also talked to Justin at comp cams and he suggested 1500-6500rpm grind with 509 lift, I'll post the durations tomorrow. The goal is to scare a certain 69 dart convertible with a warm 400. It weighs about 350lbs more and can only fit narrower tires. So the ? are how far to take the heads, what are decent specs for the roller cam and TQ stall. Any suggestions are greatly appreciated.