You Don't have to run a roller cam with roller rockers. You may be confusing roller rockers with roller lifters, two separate components of the valve train.Roller lifters ride the cam lobes. Roller rockers convert the upward motion of the pushrod to downward force on the valve.
I think it is the other way around... to put a set of 289 heads on a 5.0 block, you have to drill the steam holes in the block!! the 5.0 heads ( E7s ) are a bolt on interchange as far as coolant!! cool??
Yea, late model and 351 heads will bolt to an early block no problem. coolant holes"steam holes" will not be aligned. doesnt mean that the engine will over heat, just reduced coolant flow between heads and block in the middle cylinders. its up to you.