Somehow I knew these videos would be useful someday.
Not an LD28 but a diesel turbo in a 240z.
http://www.classiczcars.com/forums/open-s30-z-discussions/19746-biodiesel-240z.html
As for your questions I don't know if a turbo L28 exhaust manifold will bolt up, I believe the head is unique on the LD28 motors. I've seen this motors put in everything, old Holden's, 4x4s and even Z's as you can see above. I would say the weakness will be the weight of the rotating assembly.
I often see them listed on trademe.co.nz
Perhaps Nzeder on here can help out, he seems to know a bit about them.
http://www.csmonitor.com/2004/0629/p02s01-usgn.html
http://www.pape.ws/allan_and_rosanne/Z-Car_Stuff/VeggieCar/veggiecar.htm
http://www.classiczcars.com/forums/open-s30-z-discussions/31826-omg-bio-diesel-z-car.html