I am in Australia and very interested in buying a BMW E34 535i.

l have driven a few, but l have found the engine to be a bit lacking. I am also nervous about service/repair costs.

l love the shape of the car, plus all the features. l dont like the 7 series at all, and the 540i with the V12 is too expensive, both to buy, repair and maintain.

l can afford the E34, l can afford repairs, but would prefer more power.

l was considering doing a conversion with a 5L Commodore and T700 4speed Auto Conversion.

Anyone done that? I am doing it with the view of adding a supercharger as well.
You are mistake. The E34 535i is a 3.5L 6 cyl and the 540i is a 4.0L V12.
l dont think the Aus E34 is had as much power as the USA spec cars. l do not want a manual, as l have a back problem and using a clutch aggrevates my pain.

All the E34 is l have driven have been lacking in power.

Australia is not all 'Outback Roads' The road l will mainly travel on will be a sealed 3 lane highway.

l know from experience that spares are hard to obtain for the E34 and l can say with a great confidence that the 215KW 5.0L Commodore V8 is very powerful and popular with a lot of engine swaps. A cam, chip and supercharger and they are capable of over 300KW with great reliability, cheap to work on and easy to get parts for.

If l am not mistaken, the engine in both the E34 535i and 540i are both V8s. The only way you're going to get more power is if you get an M5.

l have a 91 535ia (USA version). Stock was 217 HP. Dyno measurement with a DME chip upgrade found 205 HP at the rear wheels. Do not be changing engines with any Commodores. The shortfall of the E-34 is that the Automatic had only 4 speeds. The big six 3.5 L. engine is the most reliable in the BWM lineup. Fuel economy is probably the worst, but it depends on how hard u push it & what kind of driver u are. Can ur outback roads safely hold 135 MPH?
Ca not u find a 540i with the V-8 engine & 5 speed manual ? RSVP.

BMW never made a 4.0L V12 & the V12 was never installed in any e34 car . It was never in any 3 or 5 series for that matter.
The big six 3.5l bmw engine was possibly the most reliable engine ever produced. Many owners trade in top speed for faster acceleration by swapping the differential for a higher ratio. Together with upgraded ECM chip this will give u a big bang for ur buck.
As for changing the engine to some other make the only conversion l have heard of is transplanting a Toyota supra twin turbo into place.