Part of the 1976 brochure is here:
viewtopic.php?f=35&t=148398&start=90
It gives the power as 308bhp DIN, which is about what the derated NTC355E engine made. I bet the rest of the brochure, if found says that engine was in the lorry. Our good friend ERF might have it, given that it was he who posted the page referring to the 308bhp.