I had a 393cuin with Comp Cams custom grind mechanical roller, grind 2314F/ 2318F, 250 - 258 @ 0.050, gross lift 0.640", lobe separation 110, cam in at 105.5. Used Scott Cook heads and dual plane intake, 640 hp @ 6,600 rpm, 537 lb-ft @ 5,800 rpm. This was also with Pantera Pat Mical headers. 11.2:1 compression ratio and ran on 93 octane. I idled it at ~ 850 rpm with 10 - 12 of vacuum, I was happy with the brakes. Up to you but I would not use a mechanical roller on the street, I broke a PAC conical valve spring with its no longer attached valve and later wiped a Manley Enduramax roller follower. It was good while it lasted, 21mpg on a run with FI and was fun.
Seems my engine output was slightly down in comparison with a smaller engine, smaller cam and lower rpm. Dyno headers gained ~34 hp over stock GTS headers on one run but I am not sure there was a good comparison run between Pat Micals, dyno and the GTS headers. My heads also had the incorrect exhaust valves which Scott said was bad.
Waiting for a Tim Meyer aluminium block and using Scott's recommended roller hydraulic cam and use the correct valves. That one day will be dyno'd.
Good luck with your engine choice, there are many possibilities..