i have a tow bar on myn and twice people have rear shunted me at the lights and the tow bar has taken the majority of the impact.
you should be getting more mpg than you are, have u tried tuning the carb setup?
a zetec and bike carbs although is a good option, by the time u have had engine mounts made, bell housings adapted, and the costs of all then installation you would be better off buying a ratty old sapphire cos putting the YB engine, diff and brakes from that on your car and selling the rest as spares imo