Have what is believed to be a cortina chassis on a merlin 2+2 kit car.

I have looked for the chassis number, but can't find anything, made harder by it being painted with thick black paint.

Don't have any documentation, just the car.

Any tips/tricks to identify which mk cortina she is?

 

The Cortina didn't have a separate chassis more likely they used Cortina running gear on there own make chassis. If the front tie bar rubbers (where they join the bed at the front) are of the bolt on oval type then its early mk3 if they are just round floating type it is late mk3 or mk4/5