Great cars imo, I owned a much abused (but damn quick) example about 8 years ago, like the RS Turbo I had after it, it was stolen,never to be seen again.
The engine should have a "finned" motorsport cam cover and twin coils to the right of the engine , this is the non-hydraulic tappet version of the CVH engine found in XR2's & 3's.
It also has a different exhaust manifold and system, iirc and a different cam setup that would allow high revs in the GP A racing versions - The racers produced upto 160BHP, without a turbo.
As for the op's question, iirc there is no difference in head size, so it should fit. But, you may well need to transplant the ignition setup across to the XR2 also as the timing etc is different from that of "normal" CVH's.
As I say, a lot of this is "if I recall correctly" 8 years is a long time for my memory!

I'm sure others will correct me if I'm wrong.