A TS turbo (or supercharged) is almost as powerful as a 3.0 and will be lighter; however, to do it right will probably set you back £5,000 - assuming you'll get a garage to do the work.
If you're happy with around 170bhp get the engine bored out to 2.1/2.2 litres, fit high compression pistons, and get the cylinder head ported. A freeflow exhaust and air filter will help too. This is what I'm in the process of having done to my TS - with the edition of a lightened flywheel. I should see some change from £3,000 including an engine rebuild.
If you want a bit more power then get it chipped, which will add maybe another 10 to 20 bhp
In every step, I hear your sobbing
Dare I break the shade with one caress
Dare I trespass to lift the veil
To touch the lips so soft and frail
It may be that love comes once and once only, preceded by rehersal, followed by regret.
Know well that however right a man may be they always find the fallen one guilty.
All that is required for the triumph of evil is that good men do nothing