340 T/A Demon??
If the casting # is 3577130TA its a left over TA block.
Remember that this would be the block alone. The engine would still have been built to 71 specs.
Being that it is your #s matching block you probably wouldn't want to get rid of it to someone building a TA/AAR.
If everything you say checks out it would only be a novelty. It wouldn't bring extra value.
Now if it is a TA block and you wanted to sell it, sure you could get a bit for it but then your car would take a hit in value because of the loss of its original engine.