Hang on. As you may know, older P5 (or other Novas) are not the same as the new ones (in terms of materials, not geometries). Now, none of novas (or alphas, reds...whatever) are built to last.
Original P5 and Rb Ws7 III were my favourite engines by far. Now I`m running high end OS and REDS and I can ensure that they won`t last the same.
Nevertheless its a good choice, but try to ask to somebody who uses this motor but in the current version.
Regards.