I can give a little guidance. Autozone sells an elecric fuel pump that is something like 2.5-4 psi. Seems like it was bout $40.00. That is the smallest electric fuel pump I could find. It is still like a pound or so higher than the mechanical pump at the lowest psi rating. I could not find a regulator to go down to the 1.5 psi or so of the factory pump. I did speak to someone at a fuel regulator distributorship and they said that I wouldn't need a regulator for that slight a difference. That the needle and seats would hold that much pressure difference.
I was on the verge of changing mine out and the next day my pump began pumping again so I didn't. So I can't even say I would have done it for sure because I was debating on breaking my pump down and see what was the problem to decide how costly it would be to actually repair the mechanical pump.
The repair manual will give the specs for the pump in the beginning of the fuel system section.
If you do this upgrade please share as I'm interested I just never had to make the decision to do it yet myself.
This conversion seems "do-able" but I have to say I didn't have the courage to possibly waste $40.00 and have it not work since mine began working. The last thing I need on my already overcrowded shelf is an extra elecric fuel pump. I believe that the little check valves in my pump are dirty or sticking and nothing wrong with the diaphragm itself. I think all those parts are available from Bill at satoh parts who posts on this board. You may want to rebuid yours.
And by the way for those who are saying $40.00 and this guy is stressing I'm married with three kids (one a newborn) and three horses, if anyone else out there has kids AND horses I think you'll agree ,I've said enough. /forums/images/graemlins/laugh.gif
Scott