340 No low end power

Timing and a different intake would make the biggest differences if the base shortblock is assembled correctly. A stock 340 squarebore intake would likely preform better than the torker II, especially below 4500 rpm. Put a 1" spacer on the stocker if you don't want to get a RPM or Air Gap.

IMO, don't waste time putting T/A heads on it.

Try to figure out which cam you really have. A dial indicator on a lifter might help get an idea of which cam is installed. If it's in retarded, you may have an uphill battle on your hands.

Leave the exhaust for now.