From the casual manner in which you mention putting a 518 in your 'Cuda over the winter, I am torn between two assumptions:

1. You are a master fabricater and won't have any problems slicing and dicing the torsion bar crossmember to get the transmission to fit.

or,

2. You have no idea of the challenges that lie before you.

So, which is it? One thing for sure, it's not a bolt-in swap!

Regarding the lock-up converter: There are two schools of thought, both valid. It is possible to use a regular converter, it is also possible to use a professionally built lockup converter. Either one will work, but if you go lockup you need to have someone build it who is familar with them.

There are lockup converters behind Diesels that make nearly twice the torque that your engine will. The torque converter clutch just has to be built for the job.

R.