I am not sure if this in the right spot, but I will post it because I need to learn!
I have built a C-130 Hercules that required 4 30 to 40 size 4 strokes. I have thought about switching it over to electric due to reliability issues. As of now I have a 3 wire servo wire running out to each of the nacelles. I am not sure of how I would wire this thing up if it is even possible. Would it be right to put an ESC into each nacelle with its own battery? Then if that is the case... each nacelle has a 3 wire servo wire to it... is there a junction box, or some sort of synchronize that hooks into the receiver? I am just trying to think htis out before I really get into it.

If I were you, My ESC would be as close to the batteries as practical as this eliminates the need to run the leads from the receive{servo leads] out there and I think this is recommended practic. It also means that the ESC is somewhere you can get at it for replacement, and you nacelles get very simple without lots of hatches or shells to remove. Your e;lectric motors will most likely be removable out the front without going into the nacelles after the nose cone is removed. I am working on a 1:10 scale P-3 Orion currently and that is my plan..

If the nacelle is large enough you could put the whole thing there, Bat, ESC and motor.

Yeah I think it is big enough. Using the electric would be simpler than the gas option. I wonder though about a junction box that would allow me to plug in all four control wires? I have heard Jr makes one.

It would be best to use opto-isolated ESC's and just Y them together. That way you don't have to worry about them talking to each other and ignoring the Rx. Each motor and battery would be electrically separate.

Any suggestions on the opto isolated ESC.... cheaper the better for me.

By putting the ESCs and batteries in the nacelles you have re-introduced the engine out problem that so often kills multi-motored models. The very best (if not easiest) way is to run motor wires to a location close to the ESCs which should be close to the batteries. Long battery to ESC wires create all kinds of problems with 72mz systems (I don't know about 2.4). As stated above you can then use "Y" harnesses to link them all to the rx. While opto-isolated ESCs would be the best, you can use any type of ESC as long as only ONE of them has the red power lead connected to the rx. For a variety of reasons I, personally would disconnect the red wires at the ESC plug. simply use a pin to lift the locking tab and slide the red lead out, fold it back and wrap it in electrical tape. That way you can still use the ESC on a stand alone basis later.

Perhaps you could use the three wire servo cable as a pilot cable to pull the motor wires thru.
Walt

If you have a newer digital system you can mix the rudder to the engines on each side and control the ground movement somewhat more life like then with a nose wheel! Have to do that on seaplans where you have no rudder!

For ESC's look at Castle's HV-30 (25 amps) or HV-45 (40 amps). What props/motors are you looking at? I just got a KMS 4120-480 which works great on 9S1P 2100mAh.

Wing area & all up weight decides everything. Light plane . use any outrunner. Load of bricks with a small wing. Gearboxes. Or you will need +200' to take off ....maybe. Wet fuel planes are already heavy due to vibration of the power stroke.

DO a LOT of weighing of the plane. Add the weight of the 4 wet engines & full fuel tanks as your take off weight. If you can not generate enough thrust. Nothing else matters.