Water pumps and PAS pump always need replacing in pairs. Swapping 1 or the other never works. Bit too late to tell you that now though!

Fitting the Mk7 front end will be a bitch from what I remember. All the inner wings and the bulkhead and scuttle is different from memory. I've not done a Mk6 to Mk7 conversion but I did see one converted and the person who did it said it was a right pain to do.