Hi Robin,
Interestingly you are the second person that's submitted a post about old KVA's recently. I presume you have a copy of the current IVA manual. Since the "goog ol days" of the KVA there have been a staggering number of amendments to the IVA test and many parts on an old kit would now be a 'fail'. As Mike Pass has stated, check the age of your engine and then get an engine dating certificate for it. It will then be tested to be compliant with the emissions requirements for it's age. If you don't it will be tested to current standards and it will fail.
Some areas (and there are many) that you need to check are as follows (I'm just touching the tip of the iceberg) ..... make sure all the lights have the correct 'E' markings on them and that the reverse light is wired to meet the current requirements (it must only be able to be turned on when the headlights are).
As you probably know the examiner will crawl over the whole exterior and interior of the car with a pile of radius gauges. Typical failures are the exhaust pipes, windscreen washer jets and some old wiper arms. On the inside, forget a nice row of Smiths gauges and prototypical toggle switches .... they are a fail on the radius gauges. Also beware the handbrake lever and some seatbelt metal parts. A steering wheels with nice alloy spokes with holes in them will be fail.
Let's talk side windows. Old kits had perspex side windows. That's no longer permitted, They now have to be a certificated grade of engineering plastic. You can no longer submit the car without the windows fitted. The window in the rear deck can also be a problem. On many cars this is perspex but recently there have been failures on this. I recommend that you talk to Andy Sheldon at Tornado and John Freeman at AK Sports Cars who both got cars through recently and they will be able to give you a 'heads-up' on this.
Befriending Andy & John will be well worth while .
Make sure that the brake master cylinder is correctly labelled and has a compliant low fluid level warning.
I could type many pages ....... however, you need to spend many hours going through the IVA manual and then check, check and check again.
When you are close to booking the IVA test, book a voluntary MOT test at a garage that the classic car guys in your area use. This will pick up any major issues BUT will not come close to an IVA test.
I hope some of the above points you in the right direction.
Very best regards
Steve Dean.