In my 32 I used 2" angle (3/16) that spans the frame rails directly behind the seat on the floor and mounted the seat belts to it. The angle is bolted thru the body into the frame via 2x1/2-13 UNC grade 8 bolts using existing body mount holes/nuts welded inside the boxed frame. The angle iron is viewable inside the car; function before form applies here for me.It is designed to restrain my fat butt and a passenger's in at most a moderate low speed street type crash.

Like the vast majority of older model hobby cars my car ain't designed for crash safety at the strip nor energetic collisions (over 45 mph) on the street in most cases. It is what it is ......................

Kitz