Yes, the block cannot be disassembled if still attached to the exhaust extension. Secondly, crank has to be removed to do rebuild. Third, block needs to be naked and scrubbed after boring.
You have to pull the powerhead and lay her on the bench. You will also need to pull all the pistons out and then reinstall them after new rings, bore etc. Whereas that can be done with special ring compressors, if you do not have them, you will need to remove the rods from the crank and manually reinstall all needle bearings with grease. Do not mix the bearings between rods. I use cups numbered 1-6 to hold cages and bearings. Mark rods 1-6 as well.