USD30k is a cheap price if it is what you say. - A well put together car.
Check if it is titled correctly - so that you can transfer the title to your name without having to jump through Government hoops
Give away for the A type chassis is the rear suspension - have a look at it and see if it looks like
http://www.gt40-kva.co.uk/construction.html (first pictures) and is not a good replica set up - it does work but.....
if you can get under the car and see if the rear section lines up correctly with the main chassis (Not all of them did!)
Then check in the rear is it drum or disc brakes at the rear? A lot of KVA's had Drums and these are not really up to stopping the car.
Does it have original style door handles? Quite a few used Escort parts
Does it have the normal GT40 Fuel caps? Flat top not runded? ( About £100 each)
What tyres does it have on - rim size 15 inch is as per originals but tyres are difficult to get (Avons £300 each and Khumo £70 each are the only suppliers for rear tyres)
Do you fit in the car and can you operate the controlls comfortably? Sit in the car for half an hour if you can and see how it fits - everything can be fixed but costs! (Move pedals for longer legs in the UK will cost £2 - £3k)
If you can take along someone else who knows about these cars and get an unbiased opinion it may be hard but some cars look great but are a nightmare underneath and you should walk away - hold onto your money for something better.
But if you are looking for something to potter down the boulevard on a nice day with a big grin on your face you'll get a lot of smiles for the $$$ even if it is an early chassis with drum brakes, incorrect wheels, wrong seats, incorrect fuel fillers etc. - lets face it unless you are a regular Gt40'er you will not know the difference!
Ian