A fair bit of the running gear on the 4x4 Sierras is useable.
The front hubs will need replacing as they are not suitable for the Roadster & there will be some engine mods to do.
I am sure TT will let you know the full range of engines available on the 4x4 Sierra.
If a Limited Slip Diff floats your boat the 4x4 is not such a bad option
