Most any machine shop can make a block off plate using the housing from the existing pump. They will need to provide for 2 hose connections: 1 from the tank that will connect to the suction on your new pump, 1 to supply pressure from the new pump to the valve manifold.
To determine the needed pump pressure you will first need to know jack piston size (front and rear jacks may be different), and appxoximate coach weight at the corners. you may be able to measure the ram size (the shiny part) or find a part number that can be looked up on the Powergear web site. From this information, I can calculate required pressure.
To size the pump, if we know the full load amp draw, we can look for a pump of the calculated pressure and known current draw. Amps x volts indicates the HP of the pump. Pressure x flow determine total HP needed. If the pressure is adequate, available flow will determine speed.
Get your local hose shop to make up connecting hoses with fittings. You can mount the new pump next to the existing pump (not above it) and connect the old power lines to the new pump. You will need to be sure the pump rotates in the right direction.
Good luck, but this is doable!
Not full-timers (yet)
2008 Gulfstream Tourmaster 40B, Cummins ISL 425, Allison MH3000; 2013 Ford C-Max with Air Force One, 4 wheels down; Cricket golf cart stowed inside the C-Max