It is VERY tight. I had to raise the trans tunnel a little and eliminate the pinch weld. Some folks get away with just hammering the pinch weld flat. I wasn't that lucky. What did help a lot is cutting a couple holes in the firewall to access the top two bolts. I made a couple cover plates that screw down to cover those holes.
Looks like you're getting some good work done on your 66! Be careful with the car that high in the air.