There is a detailed description of how to change the Torsion Bar Tube in Volume ll of the original workshop manual that is not bad.
There may be a few other issues.
The towers maybe small and in the past on early cars we have used modified spring perches and used the dampers ‘upside down’ so the coil springs could clear.
The RSR Trailing Arms which used coilovers on the 1973 shell had the damper mounting bracket extended
If you need to strengthen the centre of the torsion bar tube the RSR Plate is not a bad idea.
The mounting for the torsion bat covers were also reinforced on the RSR.
We make all of these strengthening plates in Domex 700MC Steel for the torsion bar centre and Tenform XF450 for the side pieces.