340 ta block whats it worth

is it a TA casting or is the casting a 340-6

The latter is not a ta block.

Decent ta blocks are anywhere from 1500-3000. Yours being the lower end more likely because of the bore.

The TA and AAR guys are the ones that are after them. If it is a TA block, get the VIN and let Barry Washington know. He may have a lead on the original car.