I assume this means UK tons (not US or Metric), so 2240 pounds.
Grade 8 US bolts have 6 Radial Lines on head and are made of Medium Carbon Alloy Steel, Quenched and Tempered with tensile strength 150000 psi = 67 Tons/square in (but this may be lower as proof load is 53 T/sq.in.)
Din standard equivalent bolts are DIN 960 with 10.9 stamped on the head having a tensile strength of 1040 MPa which is same as Grade 8.
I have in the past been sold or given bolts of lesser strength which will not do. The most catastrophic failure being those used to fit the clutch cover plate.
There are equivalent standards for nuts, and experience shows their strength varies greatly. (as recently experienced on the torsion bar puller!)
Worn or loose threads do not have a chance of transmitting the axial loads anywhere close to the yield point of the bolt. So make sure the nuts fit snuggly and have good threads. The same on the bolt, check the thread for uniformity along its length. If the bolts and nuts have been on the car for 60 years they are probably worn, stressed and stretched. This particularly applies to wheel studs and nuts; but it could be any one of the thousand fastenings on the car.
Many fastenings on a Jowett go into aluminium which is very bad at withstanding load. A coarser (Whitworth) thread should be used in aluminium, but this was not done by Jowett and often they strip, so helicoils are needed to repair.
Note that studs should be torqued up less than the torque of the nut they are going to hold which should be a lot less if going into aluminium than if it were steel. One day we may get a torque figure for every nut on a Javelin....but until we do er on the side of caution at stripping the thread rather than the part working loose (use Loctite and the correct washers all the time)
if you do not know the torque then a ring spanner gives better feel than a socket for the final tighten.
Tensile Strength: The maximum load in tension (pulling apart) which a material can withstand before breaking or fracturing.
Yield Strength: The maximum load at which a material exhibits a specific permanent deformation
Proof Load: An axial tensile load which the product must withstand without evidence of any permanent set.