I had one on my 10sec Monte Carlo. They are a great Idea! I am not sure how they would hurt a 7.3. They say the worst damadge is done at start up.
I remember a job I did where I replaced a set of heads on a 350 in a boat and when I went to adjust the valves how long it took for oil to get thru the motor up thru the push rods. That memory is what made me look into a preoiler for my $10,000 454.
I wish I had a better understanding of the oiling circuit on our motors. If I had autocad and some free time I would draw it up and have a mod put it in the tech section......Hint Hint
Eric