I did a bit of research into this change & the transition was at the end of '57 / beginning of '58 - the reason for the change was that the US mandated sealed beam headlights on all cars coming to the US & sealed beams were only available in 7"
Known 6" light car -1493*05919 - 29 November '57
Known 7" light car - 1493E*06046 - 6 February '58
The change happened sometime during Dec '57 / Jan '58 amongst the 127 cars built between these numbers, I haven't found a later '57 or an earlier '58 yet & the change was to both Normale & Veloce alike. Yes 'eyebrows' 750's ran 7" lights - all the '58 cars up to chassis 1493E06611 are like this, after E06611 the 101 styling change happened to the nose & tail and these cars are termed Interim or Transition cars for clarity.
1493E*06046 is a Sprint Veloce Confortevole, from the initial run of 50 with the framed aluminium windows, the run was built just after the Lightweights which appear to all have been 6" light cars, while the SVC's appear to have been 7" light cars - but until more chassis numbers appear between these 2 cars that's still educated speculation on my part...
Your 06227 should have 7" lights, I know that when you restored it all you could find were a pair of NOS pre-'58 mudguards which is why your car wears the smaller lights. I agree with you, I also prefer the smaller lights. You have done a wonderful job on your car and I am looking very forward to seeing pictures of it on the road !!
To clarify details, Erik is 100% correct, the smaller lights are actually 5.75" or five & three quarter inches, but are generally referred to as 6" lights for simplicity.