My uncle has a new electrical fuel pump which he is willing to give me. What should I do about my old mechanical fuel pump? Leave it on or take it off and plug the hole? Do I have to take out the rod that opereates the mechanical fuel pump?
Why not leave the mechanical pump in place until it quits working, then install the electric pump?
The proper installation of the electric pump will require some wiring and plumbing to be done, since the electric pump must be mounted as close to the fuel tank as possible. Also, it should be mounted as low as possible, and in most cases, mounting it on the frame is a bit high and will require the pump to suck harder than it should have to.
Is your engine a small or big block Chevrolet? If so, you could leave the fuel pump pushrod in because gravity will let it fall away from the camshaft. If you ever swap cams in the future, though, you may have to remove it at that time in order for the cam to be removed from the block.
If your engine is mostly stock to slightly modified, there is no need to upgrade to the electric pump at this point. I'd save the electric pump until you need it, since removing the mechanical pump may mean that it will be useless if you try to use it a couple of years down the road.
The reason for this is that once a mechanical fuel pump has had gasoline in it and in contact with the rubber diaphragm, once the lubricating fuel is no longer there, the diaphragm may dry out and crack, rendering the pump inoperative.