make sure you keep enough original bits to keep th tax excemption, there is a pionts system.
I have a series IIa wi a 2.8 daihatsu in it. I love it, the motor makes all the difference.
It has SIII axles but who will ever no, it has a siii gearbox but the only dvla mod shown is the motor.you may find it a simpler task to mate the engine to a series box
I think it may have range rover diffs but not sure, it will handle 80 on the m4 no prob but wont go up hills in 4th like many lro will.
the siii axles come wi better brakes as well. I just love my free tax disc every year,
My only request is if you do it, stick it on the web, photoes as you go, nice to see and may inspire me... good luck
keep the disco around, you never no what bits you can rob n use.