The original Interceptor was a wreckers special, a 302 c i Geelong motor that looked like a cleveland but was much weaker due to thinner castings. They also made a 351 with the same weak castings, just a different crank. Anyway it was an auto, possibly a C4 from memory and they bolted on all the "Go Faster" bits to give the effect. At the end of the movie it was truely totalled, however an enterprising bloke got hold of the totalled wreck and using another body rebuilt it and towed it around to car shows.
His tow car ended up in my workshop and was nearly as bad as the interceptor in appearance. That was over 12 years ago.