Mechanical fuel pump on a roller cammed 360?

I have no experience with the 318s and 360s once they were fitted with roller cams and lifters. I have even less experience with the Magnum series engines.
A friend may be willing to part with an '89 360 that had a roller cam but he swapped in a hydraulic flat tappet setup in it.
I'd like to use it but put a roller setup back in place for the reduced risk of cam and lifter failures. I thought I heard that these engines had no provision to drive a mechanical fuel pump.
I like mechanical pumps and would want to use one. What needs to be done to allow this? The eccentric on the end of the cam usually fits over the cam sprocket with a Woodruff key to index it. I thought the roller cams were not grooved for that Woodruff key.