Should belts for back seat

[71FormulaRA3]

Typo Shoulder Belts, not should belts. Anyone install shoulder/lap belts in a 2nd gen F-body or anything else with original lap belts? I'd like to upgrade the rear to shoulder belts for my kids when we go for weekend drives. I already have 2001 Camaro front and rear seats. I know to properly anchor the belts I'll have to add some metal for support. I don't mind doing some fabrication work if needed.

Anyone do this already?
Anyone have ideas?

I'll be upgrading the front belts as well, since they currently have the PIA non-retractable double buckle shoulder and lap belts. I will either install a set from another vehicle (not sure what yet) or the Morris belts from Summit.

Thanks in advance...