Just before anybody rushes off and tries to put a double wishbone or McPherson set up on the front of their P6.... The front inner wings on the P6 are unusually weak. This is partly because Rover actually designed progressive crash deformation into the P6 and partly because the suspension loads are elsewhere (like on the bulkhead) so there isn't the need for strength in this area.
The consequences of this show up in use even in fairly normal circumstances. There is an established failure mode on power steered cars in Australia (more stress on the inner wings due to people being able to wind the steering at standstill? Plus use on dirt roads?) of fractures in the front chassis leg. Police spec cars with heavy duty shock absorbers in the UK suffered from fractures around the bottom damper mounting and there was a factory mod - known colloquially as "hockey sticks" - which can be found in the spares manual, part no JRC 1109 page 14/70.
The "hockey sticks" are available from Colin Gould and from Alan Ramsbottom. The Rover Car Club of Australia developed a properly engineered and approved strengthening kit for the chassis rail and inner wing, including a slightly different version of the "hockey sticks", and this is available in the UK also from Alan Ramsbottom. Finally Alan has a strengthened bottom shock absorber mounting, with a proper lock nut fixing instead of the washer and split pin, which can be used either alone or with the strengthening kit.
People who have driven cars with the inner wing strengthening kit fitted tell me that the steering response is noticeably sharpened. Since the cause of the fractures the kit responds to will be flex in the area of the of the suspension pick ups, this does make engineering sense.
Lastly for those seeking to lower the front of the car. Whether you do it by fitting shorter springs or by shortening the pushrod, the net effect will be to reduce suspension travel. Whilst this is not a problem with very stiff springs on a smooth race track (track days etc), in the real world you will compromise ride and/or make the car much more susceptable to being directionally unsettled by bumps.
Hope the above isn't read as a "keep off" - the intention is to provide all the information to allow you to make a judgement on what to do!
Chris