The plot thickens on the TVR 400R. Only 7 ever built for competition. It appears the first 3 at least built in 2001 indeed have the smaller dims which it seems likely is the same as TVR Tuscan road car and what tech-racingcars.wikidot have quoted. The last 4 which I gather is the 2 Chamberlain and 2 LNT cars have the larger dims listed here:
https://auto-specs.zercustoms.com/t/tvr/2003-tvr-tuscan-t440r-specifications.html
length 4367 mm / 171.9 in
width 1880 mm / 74.0 in
height 1210 mm / 47.6 in
No reference anywhere to the wheelbase spec but you assume it has to be longer and your picture previously mentioned is the only one that is quoting a wheel base.
Check this page if you haven't already, you can really see the difference in width from the photos between the earlier cars and the later ones.
https://archive.dailysportscar.com/subscribers/cars/tvrt400.htm
So it appears there are two versions raced.
How I checked your model size was in CM by making the inertia box fit the car:
View attachment 1318069
INERTIA=1.990,1.2,4.435
My GTR2 model has the earlier width of 1.81m and wheelbase of 2.361 but it is a bit short, longer then 3.9 but around 4.1.
We can now assume that SimBin modelled their version off the earlier race car.
You could safely scale your model back a bit to the quoted 2003 spec.
As for tyre clipping the tarmac, getting the model size close to what is listed in tyres.ini solves this issue.