Flat tappet cam and Roller Lifters?

Is it possible to use the stock roller lifters with a hydraulic flat tappet cam. The reason i ask is I am using a magnum block and the roller cams that comp makes are either a little too tame or will require machining down the valve guides for clearance. The flat tappets are about $175 cheaper too. I guess it wouldnt be the end of the world to go with regular hydraulic lifters if they will work with the taller lifter bores???

Thanks for the help in advance
Author: 71DartGuy