Last time I was there, the Z Car Workshop, Underwood, Q., had a very nice RB30ET conversion 240 for sale, around A$16,000...... Hello?.........Hello?.......Would cost a lot more than that to build. There is also a red one around with a Chev 350 engine, built as a show car.
Anyway, watch out for rust. Usually better off buying something that someone else has spent zillions on the body.