some opinions of diesel

[cam.man67]

This is purely theoretical at this point, I'm not right now seriously considering swapping a diesel into my '69.

Now that that's out of the way, my question is about the 6.2 Detroit.

I had always heard that its external dimensions are identical to that of an SBC, that it bolts directly in, with no modifications structurally. Is that true?

Also, if I were to put one of these in, what kind of gas mileage can I expect with 3-speed and 3.73?

Finally, how common were the Banks turbo setups that GM offered the last year or two of 6.2 production? I see a totally new kit is something like $2200 from Summit, seems to me one that's already in a truck should be had pretty cheap.