Im not 100% on this as its such a grey area.

Ive done lots of research in to various ideas in the past.

The mods you mention would almost certainly constitute an SVA.

Most likely under the "radically altered vehicle" category

If its a rear engine escort? then forget it. its been done many times with shite results mostly. The handeling makes it undriveable
This guys driving is stupid, but it clearly displays the problems a RWD Rear engine brings
http://www.youtube.com/watch?v=bbzpSe5elsA