Get a good 6.5 Turbo core, and have it built right. You can get them with a mechanical pump. Turn the pressure up a LITTLE, advance the line timing, get a Limit Engineering built turbo, a mandrel bent 3.5" down pipe, a K&N filter, and a big Flowmaster. It'll FLY in a Blazer, especially if you put 3.73 gears in it like an M1009 military Blazer, or better yet 4.10 gears. The stock 6.2 in the M1009 Blazers runs real good with the 3.73.
With regards to the Detriot Diesel, the old two strokes were loud, and had to be wound up tight. With the right gears and transmission, they'll pull, and they'll fly. The baddest heavy truck diesel I ever drove was an 8V92TTA in a 359 Pete with a 10 over 5 Dana Spicer and 3.70 Rockwells. Put a sign on the back that read "Here kitty kitty kitty". CAT is a good engine, but Cummins was the worst junk I ever drove, on a regular basis.
The new Duramax trucks I've been driving are the best all around light truck diesels I've driven. Far better than either the Dodges or Fords I've driven. The old 6.5 we had with the K&N, downpipe, and Flowmaster pulled as good or better than any equally modified Cummins or Navistar.
I'm not much on "racing diesels", if I want fast, I want gas.