It wasn't changed to SVT. its a long story, check out "SVO'S I have to know" thread on SVOCA forums. This is a small Pro-Hawk version that I'm sure is wrong and people can correct me.
Ford was in and out of racing all the time, one time they was in it they got convenced to help on the SVO'S by a out side group Speacial Vehicle Operations. The SVO wasn't built on the Ford lines like your typical Ford cars, the SVO was built with shelf parts they had lying around. That is why the brakes are the same as the lincolns I believe. Anyways around 86 I guess Ford took another break from racing and booted SVO out the door. But they had a aftermarket parts store called Motorsports which uses the name SVO as a marketing tool to sell its aftermarket V-8 stuff. SVT is where Ford got back into racing another time I believe but this time its was there one show completely and even built there cars on the assimbly lines. Check out this SVO type car, it is what lead to the 84-86' SVO's I believe and built by Mclaran.