The “upgraded” Essex was made available as a 3000cc and a 3400cc, the latter profiled for increased torque and fitted to the Courier LDV (which was a badge-engineered Mazda 1ton pickup)
Assuming that you indeed have the 3000cc version, these were fitted with a Pierburg double downdraft carburettor, I can’t find the exact model designation, but asking the question on our facebook group is sure to get a response.
The Pierburg and Webber 38DGAS are visually similar, many hardcore Ford Enthusiasts swear the Webber is superior, but my personal experience is that the Pierburg was a fine Carb, subjectively much smoother than the webber.
But there should be no reason why the two should not be interchangeable on the same manifold