340 Engine Shake

None, at this point. Read yesterday that some small rollers don't need machine work to the block, then Seen the cam you recommended for the OP.... and then my Lil Gears Upstairs started spinning...
No fears
Their most likely talking about race applications, bushing lifters bores, oiling mod's etc.
With the correct lifter no block mods a required for the street, no black magic here, its done all time.