Installing 5 point harness into 73 TCS. Any suggestions?

[HelpMyLotus]

The seat belts in my TCS are poor representations of restraint.  They barely retract and usually fall out of the clasp on corners.  I bought a set of 5 point harnesses and want to install them.  I need the lap belts to work, would like the shoulders to work and think the center should work.  Is there safe metal to mount to?  I'm not afraid to modify or manufacture parts to increase the safety of the car.  Diagrams or photos of mounting locations would be very helpful.

Thank you in advance.

[BDA]

There is no metal on which to mount a crotch belt but you can back up the fiberglass of the floor with a piece of sheet metal to spread any load over a larger area (I never liked single crotch belts). The lap belts can obviously be mounted where the current lap belts mount. The shoulder belts can be mounted on the strut behind the firewall (that the vacuum canister is/was mounted on. That will require cutting through the firewall and the masonite and carpet of the firewall carpet. You will want to seal the holes you make to keep noise and dirt from coming in the cabin.

[4129R]

Having just rebuilt the top seat belt mounting system, it is braced back to the rear suspension by 2 strange brackets held together with 4 x 1/4 UNF nuts and bolts.

If you fit another top mounting, you should fit an eye to the firewall, and not only brace it through the firewall to the cross bar which held the long torpedo catch tank, but that brace will also need restraining by bracing it back to the chassis somewhere around the gearbox cross member. 

The side to side bar which held the fuel vapour catch tank has no strength in forward motion at right angles to its fixings, so it needs anchoring to something at the back very solid.