Hey Guys,
I don’t know about anything other than 240's, but my cars have 4 threaded holes in the chassis right under the 1/4 window that have a recessed flat spot. I mode some plates that bolted to them and welded the bar between them. It worked out to be the perfect height and position for the belts. No cutting or welding to the chassis and it unbolts with no problem. I'll take some pictures to show you soon.
Bart I will be at the MSA Autocross, trying for the first time in a year to be in control, this time with a harness. Looking forward to seeing you there.
Jeff