Its 3 Ka24 heads and he isn't producing them. Just a one off custom piece. I would be nervous using it with the compression of a diesel motor anyways.
The LD28 came in the maximas in 81-83. There's a video of a white 240z with one in it floating around on youtube. The swap has been talked about on here before too. I don't know too much about the motors but I believe they have an iron head, different stroke, and smaller bore than your standard l28.
I know you have to modify the oil pickup because the oil pan is a front sump.