As Paul said,
the GT can be had with the standard Cosworth 3 bolt exhaust fitment and can also go on the standard 4x4 manifold.
So just water and oil feed/returns to sort.
Thats probably a £1200-1500 saving alone.

I didn’t mind the lag on my .55 T34 and from looking at graphs the 3071r was maybe 200rpm behind it in spool?

Sure I will change my mind once my car is mapped on the EFR I’m just looking back in hindsight