I have an O-320 E3D, does anyone know if I can use the hydraulic model or will I have to get an electric?

The O-320-E3D will, with a few modifications, work with a C/S prop. You will need one governor drive pad, one governor, one governor oil line, two steel!!! fittings and one crankshaft plug (the plug in the very front of your crank needs to be removed and another plug has to be installed some 5" into the crank. This is fairly easily done through the front of the hollow crank and does not require the engine to be disassembelled).
I would first remove the front plug, just to make sure the crank itself is prepared for C/S operation, but, if memory serves me correct, all 320 cranks are C/S units, C/S setup or not. This would be a good time to check for SB505 compliance.
I believe hydraulic operation is generally considered the best option, anyway that is what the MT factory recommends if you have the choice.
If you are able to find good used parts for this mod., some 1000 $ should get you a long way.
I just modified my own O-360-A4J this way and, believe me, it is very easy.

Tim Jorgensen
360FB  /  45%