Hi David. I autocrossed and tracked a '65 E type ots 20 years ago and had a roll bar made for it that bolted in and out. It had a brace that ran forward onto the pass. floor, and brackets under that and the hoop that permitted easy removal. Without that forward brace (or a rear brace) no roll bar would ever pass technical inspection. This bar assembly was made by a very reputable racing fabrication shop in Calgary.
That car is gone (I went on to 10 years of vintage racing a coupe) but I still have the roll bar assembly- actually I have two hoops - one taller than the other. I'm happy to sell them, but I'm in the process of leaving for a few months to California so it would have to be in the spring. I'm at moledor
telus.net if you are interested.
Terry Sturgeon