Replacing the tap of the bathtub

It was found broken earlier today... it's a public holiday today but thank God, I managed to find a shop to buy a replacement, so the question is, how to replace it?

I did measure that the distance between the two water pipes (hot and cold) are around 6 inches. So I went to the shop and asked, whether it's standard or not, the answer is positive. But then you know what, you can hardly be exact especially when the water pipes are coming from inside the wall! So, how to accomodate the difference?

The key lies in the following picture:



Yes, you can rotate it along with the threaded pipe from inside the wall, so the difference can be accomodated.