I think the early Monsters came with a vacuum type fuel pump. The steel fuel line mounted inside the tank may be different on a vacuum fuel pump Ducati versus a electric fuel pump Ducati. Less length, different filter arrangement. Maybe someone on the Monster forum would know more.
If your bike is fuel injected, no, a vacuum pump won't produce enough pressure to run fuel injection.
When I had my 99 Monster 900, it used a vacuum fuel pump to keep fuel in the carbs when the fuel level dropped below 1/2 tank since the carbs were slightly above the middle of the tank. I used a universal vacuum pump designed to work in lawn tractors and racing go-karts. Cost about $20 on ebay and worked great. The trickiest part was finding a place to install it.
Is there something wrong with your electric fuel pump?
If you're having problems with your stock fuel pump, I think an external electric pump would be a better option than trying to fit the vacuum one. I believe ClickityClack is right, the vacuum pump most likely doesn't produce enough fuel pressure.