I don't have an answer for you Tommy.

I have the same truck, and I've had the same thoughts about seats with integrated seat belts. You might also look at seats from a 2004-2007 Cadillac CTS ( which I used to own). It also had the integrated seat belts and I think the rear seat back is a bit thinner in design than the Silverado seat, which might fit the tight space in the TF. I also thought of reversing the seats. Driver for the passenger, and passenger for the driver. Only because the shoulder harness retractor is a bit bulky in the corners of the cab.

For now, I'm using the original seat without any seat belts. That might change once I know how well the drum brakes work when I get it on the road.

When God gives any man wealth and possessions, and enables him to enjoy them, to accept his lot and be happy in his work�this is a gift of God. He seldom reflects on the days of his life, because God keeps him occupied with gladness of heart. Ecclesiastes 5:19-20