are there many parts from the FWD 6g72 that would fit onto a RWD 6g72?

Try again.

ok, the 6g72 is found in "Front Wheel Drive" transverse mount vehicles e.g. the aussie mitsu magna, and also in "Rear Wheel Drive" longitudinal mount vehicles e.g. the aussie mitsu triton.

I was wondering if the block, heads, manifolds etc. are interchangable

Oh ok, I believe so then. As long as the engine code is the same. That last number changes between models.

Also, if you have DOHC and a SOHC then No but DOHC and DOHC yes and SOHC and SOHC yes.

thanks mate, as I have a 4x4 triton with the DOHC 6g72 which is quite lazy, and a magna with a DOHC 6g72 which goes very well for what it is, & I'm gonna be getting rid of the magna soon so I was hoping a bit of swapsies would be possible, if I can change almost the whole engines it would be great.

The weight difference is the reason. Not the motor.

I beg to differ, as my other MK triton is the exact same model purchased the at the same time and has done similar kays but has been driven around by me for work, maybe I have a bit of a heavier right foot than some, while the lazy one was worn in by a worker who babied the vehicle and just put putted around and as a result it is way down on performance and doesn't look as if it is capable of recovering without a rebuild.

not all engines from the same factory line are created equal, and the way they are worn in makes an even bigger difference

That being said the one that was put putted around in is going to be the one you want.