[MG mad]

I wouldn't go down the route of popping a ZS body on a ZT 260 platform for a couple of reason: wheelbase on the ZT is about 120mm longer (and track is wider but that's easy to deal with), and the ZT engine isn't the greatest thing in the world. I say this as someone who owns (or, more accurately, who's wife owns) a 260 which we can't ever see us selling as it is a fantastic car, but the engine uses technology that is about as current as 80's fashion. There are far better options for engines around, especially when you consider the weight.

Having said that, there are brand new rear stuff ups for the 260 floating around which have everything you'd need for the rear end if going RWD, and if you can find a front subframe from a 260 you could use that together with a 4V Ford engine as the block is basically the same as the 260's 2V engine, but alloy. That also gives you 320hp in 4.6L form, and more in 5.0 and 5.4L. Then you just need a gearbox (the standard box in the 260 is ok, but there are much better options around that Ford have used behind the 4V engines) and lots of fabrication.