Clive Du Cros' heavily modified Jag engine put out around 400hp. Even in standard form they put out around 250-300hp. More than sufficient for fast taxiing I would have thought
If you were prepared to sacrifice performance and internal originality but maintain the external form couldn't it be built via a PFA Permit with a couple of Rover V8 engines? There must be more bodies who would give time/money to a flying replica than a to a static one even one as worthy as this.
The Rover V8 was used in a Chipmunk once. It looked lovely. Mmm maybe I'll start a thread about that.