To fit a type 9 to an essex correctly you need a bellhousing from a Mk1 2.5 or 3.0 Granada or as you said an alloy one from Burton.

You can use your bellhousing and modify it to take the Type 9, you have to machine out the hole in the middle where the input shaft gos re drill the mounting holes and nut and bolt it together, although this has been done before there is a risk of it cracking the bellhousing as the hole end up in a thin part of the casting, you might have to cut abit off the nose of the input shaft aswell depending on what T9 you have and also check the spiggot bearing in the end of the crank i cant remember if you have to change that as well.

The bulk head and tunnel will also need cutting out and making larger and the hole where the gear stick comes through moved back, when you do this you make sure the heater box gos back in before you weld it all up as if you make the tunnel to big it wont fit back in i know this from experance.

You will all so need a gear box mount you should be ok with the capri one just drill and bolt it through the floor using big washers on the inside.