1956 Ford f100 automatic transmission

[greenf100]

Hi I am searching for an automatic transmission for my 1956 Ford truck . I have the outer casing but internals are shot. Wanted to know the best sources to find one or if anyone here has one for sale in good condition . I want to keep this as original as possible with no modifications . Any leads or info on sources would be greatly appreciated. It was my grandfather's truck and want to get it back on the road this year Thank you!