as it happens, I'll be in a position to take some measurements in the next few days - for the BMW lump at least. Mind you, jumping out of the Holden into a BMW V8-powered car it does seem a bit anaemic.
Whilst the Holden is a great drive and handles very well ( at leaast on a par with a BMW ), getting ionto the Omega makes me realise just how "top-class" its handling really is.
Holden with LS1 is about 75kg lighter than standard MV6 2.6.
You're always going to struggle to find a decent V8 available with a proper gearbox. Manual 540s for instance are a whole lot more expensive than autos.
Another option would be BMW straight six, which is doable with even less effort.