the bore on a 1.5 and 1.6 are the same, the stroke is slightly different so you will need to confirm the compression height of TDI pistons for your bore diameter. as for the TDI head fitting on, I am not sure if the valves will fit in the bores as I have not tried it. I am sure someone else on here can help you with that. I can say that if you try it you are going to want head studs and the head bolts in a 1.5 are 11 mm, the TDI's are 12 mm if I recall so you will need to do something to center the head bolts up in the bolt hole of the head.
later
jkeiffer