So.......... on my 1985 Thunderbird Fox I am preparing to swap out the Vacuum Brake Booster to a smaller diameter unit (running a 351W motor and need more valve cover clearance), so I need to confirm that the '93 Cobra Booster, which is smaller diameter but a little longer, is the correct booster. Correct? I've also read that widening the mounting holes on the firewall will allow easier installation. I would love to run the Hydroboost system but for this application I believe the Vacuum unit will be adequate since I'm not running a bunch of lift or duration on the cam. TIA