I think the confusion between the 3.2 and the 4.0 engines, in this case, stems from the fact that Jaguar were owned by Aston Martin when developing the XK8. This was also around the same time Aston were developing the DB7. The 3.2 litre supercharged 6 cylinder in the DB7 was originally intended for the XK8, but Aston 'Stole' it. Quite why they went ahead and developed the 4.0 V8 instead of using the original engine I don't know, but I'm sure someone out there knows.

The 3.2 litre engine was available in the XJ8 (sedan) model only, and never intended for the two-door XK8. It is quite incorrect to say that Jaguar was ever owned by Aston Martin; they were both owned by Ford, and the V8 engine was developed solely by Jaguar for the XK8 and future XJ series sedan.

The Aston Martin V8 was designed by Tadek Marek, and has nothing to do with Jaguar or Ford. There's is a totally different engine, and I think better designed, and better sounding too.

The Tadek Merek Aston V8 engine powered Astons from the '70s through to 1999 (The twin Supercharged V600 Vantage being the last car to use that engine).

The V8 in the Aston Martin from 2005 on (i.e. the one in the smaller, confusingly similarly titled 2005-year "V8 Vantage") is a variation of the Jaguar V8 in the XK8. It was designed and developed by Jaguar. It is not used in any Jaguar or Land Rover products.

The straight six engine in the DB7 is also a Jaguar engine, although Jaguar never used the 3.2 litre supercharged engine, but a 4.0 supercharged version in the X300 XJR.