opinions wanted on motor build

[292farmer]

hey guys hoping for some idea as too how much power my motor may make, its the stock motor in my 1972 GMC c25 w/4spd manual, dana 60 rear w 4:10, my motor is a 292 inline 6 I'm boring it .060 over to 3.935in with a stroke of 4.15in the heads are going to be shaved .060 and my compression should be around 9.5-9.75 with 92 octane and hei dist off a 75' or later i6. also the heads will have the valves upgraded to 1.94int/1.6exh with a lump port kit im going to be using an offy 2x1bbl intake with stock style rochester 1bbls im gonna have a garage tune them and dynomax headers with 2.5in exh the camshaft is hopefully going to be cliffords its their cam that specs out as .573" lift 270* dur adv. and 240* at .050", the guy at clifford said id see double my hp&tq with this combo, which means with a stock of 170hp and 275 tq means id be pumping 340hp and 550lbs torque! i havent built many motors this being my 2nd 6cyl but that seems like a lot for those upgrades i was thinking between 275-300ho and around 350-375tq, does anyone have an idea as too which is closer? will this make 300hp at all? my goal is 300hp so i just want to know if ill actually make it or whether the guy at clifford was just trying to sell me a product a little overinflated. thanks for any input, suggestions, or comments!! also are the weber carbs maybe a better choice for power and economy, then the rochesters? or does anyone have any ideas for other good 1brl carbs?