I can tell you that the TB42 with all ancilliaries is about 225kg. This includes flywheel, clutch, A/C pump, power steering pump and alternator, both manifolds and carburettor.
It has an alloy head, so will probably be a bit lighter than the TD42, but i wouldn't have expeceted nearly double.
For interest, i once did a conversion on a 1969 Lotus Europa. From an all-alloy Renault 16TS engine to a Toyota 4A twin-cam engine. The toyota engine had a steel block and an extra cam, yet it was 1kg lighter than the Renault.
Mag ons ons kenniskry met lekkerkry aanhoukry.