hey man how youve been? whatever happened with that 347 you were putting together with those heads i sold you? the 1.72 rockers will bump the lift about .30 give or take but like everything to gain something you must give up another and in this case is valvetrain stability and if you break something the damage is greater with the 1.72 rocker. i personally wouldnt run them but ive seen other people do good with them. good luck.