That clears things up.
Block/head is a MK3 Escort unit, but it came with a Ford VV carb like the smaller 1.1 and 1.3 engines had. The engine had 58 kW/ 79 PS.
This one has been converted to a Weber 2V carb like it was used in the later MK2 XR2 with the lean burn head. It would be good to know what kind of carb was used.
There were a lot CVH engines out there with a 2V carb, (inlet manifold must be from a CVH) from 1.4 with ~70-75 hp to the XR2 MK2 with 97 hp. 1.6 CVHs with a 2V carb range from the mentioned 79 to 97 hp. The carb being too small (maybe a 1.4 unit?) might cause your problems.
The air filter box is a OHV one, that's the reason why it was cut.
Do you REALLY want to keep it???
1. take the head off, put in a new head gasket and new valve stem seals.
2. take the carb off, check if it's big enough, XR2 MK2 had a 28/32 TLDM, not sure about the MK3 Fiesta S with 90 hp. If it's big enough, give it a full service.
3. either go for a later water pump and get the MK3 Fiesta hoses you need OR keep the water pump and get the Escort MK3/Fiesta MK2 pre-86 hoses for the heater matrix (to/from water pump and thermostate housing)
4. I'm not sure about the compression ratio, but it SHOULD be the same as the XR engines had (9,5:1). 79 hp could be the result of the smaller VV carb or/and a different camshaft. Get a XR2 carb camshaft or an aftermarket part. I'd go for nothing too crazy, maybe a 285 or 290° one. People say Newman sell good camshafts for the CVH.
Would a engine with BRA code drop into this car?
Are heads/bottom ends interchangable?