I have a 1962 Beetle the steering is very nervous / light, the steering wheel moves slightly left and right, I have replaced the tie rod ends king pins are very good, damper is new and so is the TRW steering box .

Any ideas to heavy up the steering ? is there a better steering box ? Thanks.

What pressure do you run in your front tires?

when was the last alignment done

If everything else is correct you could fit a set of castor shims under the lower beam tube, that will increase the castor and make the steering heavier. https://www.justkampers.com.au/caster-shims-for-vw-beetle-1946-1998.html 

is the rear end lowered

155 x 15 (small size of tyres & hi pressure and type like non-radial could be factors

Front tyres are 185x60x15 rears are 195x60x15 I run 25psi in the front tyres I will look at shims ,wheel align was only two weeks a go !! Thanks.