I found a Model T Chassis on Ebay and the seller also has a front Axel and a steering collum up for sale and at 3am it seems like it could be a fun project, But I don't think a model T would pass an IVA. The Chassis has a V5 with it and I was wondering how much of the car would have to be genuine Ford Model T? From memory I've a feeling that a propper T body and Suspension would be enough (And that modern repro ones would count) and I could somehow attach the engine and Transmission from a Scorpio but I don't really know. There seem to be alot of cars on Model T V5's simillar to this, or have I completely missed the mark.
In the resto world a V5 and a fraction of an original seems to be enough.
Most resto's if put through the IVA process would not get an original reg.
If its a real restoration back to original you would not need seatbelts or lights
It's a minefield.
The unmolested chassis is the most important thing. Nothing much allowed, small extra brackets, but that is about it....
The reason restorations get away with being just a few boxes of bits is that you ARE allowed to use a brand new (though officially not a secondhand or
even reconditioned chassis)
That means that every time a kitcar has changes made to its chassis it should have a fresh IVA
In reality it is not usually an issue, as long as things are done sensibly.
Have a look on the dvla website, it is all on there.
If it has a v5 then theres nothing really to worry about. An old car like that is unlikely to be questioned on whether its 'all
original'!
There are alot more serious 'radically altered vehicles' out there that havent been IVA'd that VOSA would be more interested in!
If you have a genuine V5 and it looks like a model T, who is ever going to check? It could get very difficult if you ever have a crash as your insurance would disappear in a puff of righteous indignation from the company.
Just don't fit a Blade motor and you'll be fine 
in its most basic form of an explaination, if its an unmodified chassis, then it doesn't need IVA, after that, do whatever you want with it 
The guy is looking for £1200 and T bodies aren't that hard to find. Nothing the DVLA put online makes any sense to me but does look like I could do what I was thinking (Modern Engine/Box with a standardish, slightly hot rod body) and I've found a few cars simillar to what I'd want at the end that have 20's T V5's. Might be worth a punt.
Or you could go here
http://www.direct.gov.uk/en/Motoring/BuyingAndSellingAVehicle/RegisteringAVehicle/Registeringakitcarrebuildorradicallyalteredvehicle/DG_191158