The power gain from 9.2 to even 10:1 is minimal. You will likely end up with a power loss. Dome piston design and hemi head is very prone to detonation.
Cylinder head work - by someone who knows what they are doing will help.
Dual weber intake manifold also will add power.
Adjustable cam gear- perhaps, but why?
Are you changing camshaft?
The UK camshafts will not work in US 1.9 head. You will have to use a 1.6 head to use UK cams. (The camshaft journal sizes were changed on the 1.9.)

Steps I would take:
Ported cylinder head
Header with larger exhaust piping diameters.
Intake manifold - dual weber or individual bike carbs (if you are familiar with tuning them).
Camshaft change (if using 1.6 head) Do not go crazy on camshaft timing either.

Cheers!!