1957 Buick Roadmaster 76R A/C Car Needs Restoration

My dad purchased this car roughly 10 years ago. Unfortunately, it didn't come with a title. Just recently we started to work on the car and the title issue. We had a State Police officer come out and verify it wasn't stolen and that the vin tag matched the vin on the drivers side frame rail. Everything matched and came back clean. The officer filled out a form that needs to be sent off to the secretary of state. This is where we stopped. It will need to be appraised and bonded. All of the paperwork will then need to be sent to the secretary of state. They said it should take roughly 60 days to receive the title once everything is sent in. We just do not want to go through the extra hassle because we aren't going to keep it anyway. I will supply the new owner with all of the paperwork we have. My dad does have a title for a 1957 Buick with a different vin which could be included with the sale.
This car sat for decades before my dad purchased it. Within the last year we got it out of storage and starting working on it. The original engine was taken out by the previous owner and replaced with a 1958 364 that supposedly came out of a station wagon. I oiled the cylinders, installed all of the throttle linkage, replaced the accelerator pedal, rebuilt the carb, cleaned the gas tank, replaced the entire exhaust system, replaced fuel pump and lines, points/condenser, and wired up a push Button starter switch. The car does run and move under its own power. However, I was not able to get coolant to circulate enough to open the thermostat. Seems like there is a blockage somewhere. I'm guessing the heater core could be clogged? It does blow a fair amount of smoke out of the exhaust pipe. I’m unsure if the dyna-flow transmission is original to the car. The master cylinder is brand new along with all four brake cylinders and a few brake lines. The car leaks transmission and differential fluid. Again this car sat a long time so EVERYTHING will need to be gone through. The goal was for us to get it to run long enough to drive it on and off the trailer, which we are now able to do. There is some rust in need of attention. The left and right rear wheel house and part of the trunk pan (where the spare would sit) will need to be fixed/replaced. Also, There is an area on the passenger side frame rail that might need attention, see pictures. Ebay limits the amount of pictures I can post but I would be happy to send any addition pictures upon request.