Is there and any adaptors available that allow you to plug a MS2 into the j3 port of an el falcon so you can keep the standard features and edit or add what you like from the MS2 software. I have an auto ecu with manual gearbox and I'm told I need a manual computer to solve my idle problems because I need the 'dashpot'. If I can't get my hands on a manual ecu, can I setup a dashpot with the megasquirt so get the car to idel like it should?

You cant piggy back the EEC-V with the MS2 using the j3 port.

You will have to piggy back it by cutting into the stock harness. You can share the sensors, but you have to cut the injectors and use a different RPM signal for the ms2 to work. leave timing to the EEC-V or ms2 your choice.

but seeing as your car is manual you can just run the MS2 standalone. and completely remove the EEC-V. using the ms2 to control spark and fuel.
you might loose some functions of accessories like trip computer etc.

Any suggestions on where I should buy the Wideband o2 sensor from and where I can get information about installing it?

try here >>>http://www.diyautotune.com/catalog/wideband-systems-accessories-parts-c-23_45.html

is the falcom EEC-IV? If so there is an adaptor board.

For the record MS1 will do what you want.