The inlet manifold on the 1.3 has smaller ports than the 1.6. The 1.6 inlet gasket that I had wasn't a great match to the ports so I opened up a 1.3 gasket to fit.
Modified gasket on 1.3 inlet manifold:
Then stuck the manifold in my cheapo Workmate copy and broke out the flexidrive and a grinding tool
I opened up the holes to the size of the gasket. There is a galley on one side of each of the ports, I just smoothed this out down to the level of the casting mark.
On a carb engine the 1.6 fuel pump is bigger too so the manifold also needs a little clearancing in that area too
The alloy is really easy to work with and even taking it steady it was only about 1/2hrs work.
Surprisingly the 413 exhaust manifold was a good match to the 1.6 head so I didn't touch it, I used the 1.3 exhaust gasket too.