I used to play with the 2.8's back in the day and I upgraded my 83 to a 86 block. Seems to me the biggest problem I had was the oil pan. I had to use half the oil pan from the 83 and half the oil pan from the 86. I did this in 88 so I really do not remember the details. I do remember it took me 3 weekend. At that time I could do a straight swap of a of a 2.8 in about 6 hours so there was a lot of fabing. When I was done it looked like a stock 83. I did not have a FI system to put on it just the new GM long block I got for free