Nah thinking more of 734s, as my head would need more work to make the best of the 809s and quite frankly you're having a giraffe if i'm spending £1k on a new head, the 734s should give the same top end power(probably closer to 190bhp) with higher torque and a better spread, should get rid of my flat spot at 3.5k too. you can see on the graph the jump at 7k, it should keep going up but the head is limiting it so it dips down again.
That £1k could be spent far more effectively elsewhere i reckon, like tarmac spec suspension and track days
Edit: forgot to mention about the diff
Updated that.