Just found this piece on type 49 shells..
to quote
Just for information, (back in the 70's) when the bodies used by AVO, they were heavy duty "export" shells, so they had the double skinned inner guards and chassis skids,
but the rest of the "type 49" conversions were carried out by hand.
This involved using a Gas Axe to cut holes in the rear chassis rails for the anti-tramp (radius rod) brackets, which were stitch welded on.
Gas Axeing the gearstick ring from the top of the trans tunnel and enlarging the hole, before stitch welding a new plate on further back to cover the longer gearboxes
Drilling a hole in the upper bulkhead for the hydraulic clutches (which they also did on RS2000 shells, even though it was not used)
Stitch welding on the heavy duty exhaust hangers
and
I think they also brazed the studs into the boot floor for the stone deflectors, which were only fitted to early cars, even though the studs were on all cars,
I never got a definite confirmation on that one though, but it does look like it was done by hand