How hard is it to put a BBB in a 1950 series 40

[Topless64-455]

I have a friend that has one and he wants to put a mild engine into it with headers. Anybody made the switch and have pointers. Thanks

[64Electra]

Lotsa fun!! Gotta have to get rid of the torque tube and pretty much everything else underneath. Is the car a stick or dynaflow?