You are probably setting yourself up for a lot of work unless you have both vehicles side by side to do the conversion, many years ago I did it with two Peugeot 504s, petrol automatic to diesel manual, on that model everything interchanged and the only thing I had to add was a return pipe for the diesel to the fuel tank.
Out of choice I would go for the slightly later 1.9 diesel, pre ecu if possible as 1.7 now a bit obscure for parts etc. one of my daughters had one as her first car, but rust got it in the end.
Another point is the weight difference affecting suspension/handling etc. Also the legal requirements, insurance, details in V5/logbook etc. etc.emissions laws etc. Insurance companies would like proof conversion was carried out by qualified engineer etc. I suspect the legal aspect these days will prove every bit as hard as the mechanical challenges.