Folks

I am at the stage in my build where I am putting in the seat belts.

I want to fit lap/sash retractables in the front and rear seats, with a lap belt for the centre rear.

For the holes in the floor, mounting plates are easy.

For the shoulder mount points, and where the actual retraction box is.
For the front, getting a standard mount plate into the b-pillar is problematic. I would have to cut the pillar open, and re-weld in the plate. Ugly at best. Is this the only option?

The retraction box would go down at floor level into the b-pillar and bottom sill point next to the seat. Would there be enough space in there with the standard seats?

For the rears.
The shoulder point would need to go into the c-pillar with the retraction box under the parcel shelf.
Do you think the c-pillar would be enough, and how do you think I should mount the retraction box under the rear shelf.

Cheers
reubs