Hey guys I have an 04 Nissan 350z convertible and I am trying to replace the motor that is seized. Becuause I can not turn the crank to remove the torque converter bolts. So I have 2 options? Pull engine with torque converter attached carefully or remove oil pan, remove rod bearing caps and knock pistons up to free up crank. Which is the way I have chose but having difficulties getting upper oil pan out of car. Any best practices? Or is it easier to just remove engine with torque converter attached?

If the engine is seized you are gonna need to pull it, so why try wrestling wiht the pan in the car, drop the trans otu the bottom and pull the engine out the top, Once it's out you might be able to get all the bolts out fo the flexplate with end wrenches, it not torque convertors aren't usually expensive and your replacement motor just might come wiht one, or it's a good to time for a manual conversion

Since I have to replace engine anyways and already have all trans bolts removed already could I Lower The back end of the transmission down a little bit and pull the engine straight out with the torque converter still attached?

Yes, incompetents do it all the time and not that hard. I say incompetents, they know no better, you have a good reason not to remove it. May have to loosen engine mounts to let back of engine flop down a bit more to clear the convertor. For SURE expect a flood of oil even with trans drained. You can take apart that way but you will NEVER get it back together the same way.