Nice looking Demon you've got. On the converter, I would, like RRR guess somewhere in that 2200+ range.
On that note, why trust something built 30+ years ago. It was probably built by the converter division of Man Mac transmissions who are no longer around.
You've invested a lot of time and money into the engine, so don't cheap out on the converter.
Call Paul at T.C.S., 604-533-8675, give him all the specs you've got, tell him what your plans for the car are and he'll get you the right converter.