Bronze Distributor drive gears for Roller Cam

Any help would be appreciated for the following statement. You can see my 440 mock up in pictures below. I have the bronze distributor drive gear for it and had one in my previous 340 roller motor. All of the small block and big block books I have read always state that you must run one otherwise you will find metal shavings in your oil pan. I understand this plain simple fact. :stop:
Can any explain the specifics as to why? :stop: One further question would be, do I need to run a bronze tipped fuel pump pushrod or can I run a regular one? :read2:

First Pic of almost complete mocked up motor