3-Point Y-Harness Lap Belt Mounting Location?

[66S]

Maybe the 74 runners needed more meat rather than the earlier ones. Those lwb pre 74 runners are not thin.

[blue72s]

Those lwb pre 74 runners are not thin.

I agree. I think the SWB runners (both comfort and pre-68 Recaro sport runners with tabs) are thinner.

[blue72s]

if test was mid June 1975 perhaps doing crash test of the coming model year 76?

Can you post the article here? Porsche did not change the '74 runners until about 1985.

[911MRP]

Dint think they changed the rails they made the rails out of stronger material. Maybe not possible to tell the difference if it was just the material changed ie different metal? .
It’s not an article it’s a one liner about dated production change . It says

“ Jun 16, 1975, Seat rail (PN 911.521.491/501/502.00) changed to a
stronger material as PTL 8001 crash tests found rails to
open and bend”

As said, not sure it is relevant but does give pause for thought if Porsche found a weakness in the seat rail in a crash test. I think this is date material change took effect rather than date the of failure in test.