No you do not have to unbolt the TC, but you may have two problems. The first one being that the TC contains transmission fluid, and as soon as it slides out of the transmission, it will pour out onto the ground. You will need a catch pan to do this. The second problem will probably cause you the most trouble. In order to remove the engine in the way you describe, the TC must be pulled straight out and the engine must also be tilted upwards from the motor mounts in order to do this, which will cause an aligment problem, especially if you decide to try to put the engine back in this way. You may also encounter clearance problems in the front of the motor as the TC adds an additional 8 or so inches of space that must be cleared to get the motor away from the firewall. Finally, when reinstalling the engine, if you still have the TC attached, you need to index it to align with the keys inside the pump drive within the transmission. Ordinarily, you would simply slide the TC on and rotate it until it aligns and pops in. Then after the engine is in, you can rotate it to align with the flywheel, however with it attached to the engine, you will find it a little difficult to rotate the engine easily to do this. It will, in the end, not save you any more time and you will most likely end up taking the TC off in the process because you will have clearance problems. My advice is to leave the TC stuck in the transmission (unbolt it from the flywheel). It has been normally done that way for years.