You'd struggle to buy a Vette even then on a UK salary in 1968 - an average annual figure in the UK (for 96% of the population) was £1,144 pa)
Wheras in the USA that average figure was $5,571.76 pa. Convert that to pounds at the £/$ exchange rate in 1968 and it equates to £2,331 pa in the USA.
So more than double the earnings at the time here in the UK. Purchase tax here in the UK 1968 for motor vehicles was increased by a few points from 27.5% to 33 1/3%
Don't know what import duty would have been. UK petrol was the equivalent of 25p per gallon (or approx 5.5p per litre) in the USA it was 35 cents per US gallon (about 22p for a 'smaller' US gallon perhaps)