School: kz550 cylinder block differences & Swaps

Looking into my 615cc build on my 83 kz550A and was wondering what other cylinder blocks can be swapped over (if any) to my bike. I want to maintain the same carbs and I know the blocks get finicky with the 83 carbs (from what I have heard). Don't know if any 81-83 blocks will work with my KZ heads such as the "B" engines and other models like the LTD. From what I have heard, if I wanted to go the GPZ route, only the 81 GPZ head uses a cam that allows for the mechanical tac like my 83 550A. Looking for the least amount of down time and to have a block ready to go would be a plus. OR, Plan B is to drop in a complete 750 motor from a 82-83 kz750 F or L3

Any input is appreciated. Thanks, Brendan