I believe the 200-6 is physically larger than the Triumph 6, although I never bothered to measure mine. The 6 is a tight fit in a GT-6 engine bay, and not too spacious in the TR-6 bay. You need the 'power bulge' of the GT-6 bonnet (hood) to fit the 6; a Spitfire hood won't close over the GT-6 engine. The TR-6 engine and GT-6 engine share the same block, the 2.5 litre was a stroker 2.0 (originally a Vitesse 1.6 IIRC).
I used to specialize in Spitfires and GT-6s (and had a Spitfire-6 which I miss greatly...and my dad still has not been forgiven for selling the wreckage while I was at sea).
The downdraft carbs will add more height to the engine as well, so you may need to find a way to increase clearance; again, I don't have comparative measurements so I have no idea by how much.
Bear in mind that people have stuffed Jag V-12s (just cut the nose apart and let the front cylinders stick out!) and small block V-8 engines in these, so anything is possibel; IIRC most of the conversions used hood scoops for clearance.
I had actually started making CAD drawings of the Spitfire frame as I had wanted to try fitting a modern engine in one; I was considering a Nissan 300ZX for a while but they're quite heavy and I was afraid handling might suffer, the poor little things understeer as it is (until the rear axles 'jack up', anyway). An RX-7 was another thought.
If you must add power be sure to tame the rear suspension--A 'rotoflex' GT-6 rear with the lower wishbones is recommended, or at the very least a MK.3 GT-6 or Mk.4 or 1500 Spitfire (both post-1970) with the 'free' rear spring.
Good luck! If this fits well, then maybe a crossflow with triple webers is in my future....now to find another Spitfire...
Ben
