I think you'll see if you look closely, the photos are from different stages of build; one is pre scuttle fitting for example, where as another clearly shows heat cycling on the manifold.
It's not a regular chassis that's for sure, it's also got diagonal bracing in the nose. The Duratech in the Sport 2000S chassis was virtually solid mounted IIRC, and even had cross braces too the front of the block/head area.
Its a real case of buyer beware with cars like this; it might be an absolute cracker, with only a few fiddly but straightforward jobs doing for IVA. (They can't be that easy, easy, or the seller would do them/pay for them to be done)
Or it could need major strip down because something basic has been forgotten or done wrong. You'd really need to have a good telephone conversation with the seller and get a feel for them personally, then make a list of what they think needs doing for IVA.
Brush up on the test yourself, and have a viewing as of you were an IVA inspector.
The very fact that the work has been done at Northampton, that has been claimed to be done, is probably it's biggest plus point. Particularly if NMS remember it and will talk to you about it.
BUT, no matter how well built, I wouldn't pay within a grand of on the road price, even if it was spectacular, if merely "good", I'd want more than that off the normal on the road price. Even if little needs doing, don't underestimate the cost of IVA and registration.