So, sorry to resurrect this thread again guys, but.....
I'm concerned about the change to ST170 engine from a 1300 in my Mk2 Escort estate, and wondered if it might be wise to try and get it MOTd first, and then register the engine change afterwards. Will the inspector reject it for having the wrong engine, or merely test it as normal?
Looking on various forums and checking registration numbers of pictured vehicles, it appears that a number of people are actually running classic fords with MOTs that are still registered with the original lower capacity engine, so that suggests that it is possible. I'm intending to get mine correctly registered (don't want to risk driving it around with the wrong engine and having the insurance company play up) when it's finished, but I just want to try and make it as painless as possible.