Hello,
The 6.2 was avail. in 1/2 tons in the 80's. It will bolt up to your GMC bellhousing ok, and the motor mts are the same a V8. But there are some other problems that need to be addressed. The diesel needs a big radiator with an oil cooler. You might be able to use one out of a diesel equipped truck but measure first as they are very long. You will need a very strong starter and there may be a problem with the clutch cross shaft ball stud mounting. If I can find solutions to these problems I might put a 6.2 or 6.5 in my 66 C30. Good luck, Mike
