Quickfit Harness

I only have a 3 point seatbelt in my 73 scamp. I feel that it would be better to have something better to hold me in the seat. I am not bracket racing and should not be under 11 seconds but mid 11s is doable. I do not have a roll cage or bar to mount a harness. my son told me about this as a possibility. Has anyone seen or used these? What other options are available for stock interior??967_quickfit_asm_b.jpg 967_quickfit_installation_graphic_b.jpg