If the Ford Escort estate/ van mk 2 petrol tank was fitted as the build manual described then it was fitted from under the car and after removal of fixing nuts and bolts can be dropped and removed from underneath. This tank has a flange all the way around it and this is bolted to the two cross angles. I have no knowledge of fitting the tank you mention. However you know the saying, if it fits the hole!! You may have to consider a different mounting method, perhaps hang it in on metal/ stainless straps.