As I understand and please correct me if I am wrong here , some versions of the top end cassettes that Tascam produced were supplied with phono connection as standard or you could buy an upgrade kit in order to add balanced XLR ins an outs.
From the original data I have
The TASCAM LA-322 balancing kit lets you add balanced XLR I/O to your TASCAM 322 dual-well cassette recorder. The LA-322 balancing kit includes two panel-mounted XLR inputs, two XLR outputs, and an input switch that lets you select between balanced and unbalanced.
I think the kit contained a back panel, screws and two pcbs with all the connectors and where to put the wires in there are only 4 plugs two red (3 pin and 2 pin) and two white (3pin and 2 pin) so they will just plug into the pcb, I would need to look in a manual but I am guessing its going to be the empty plus with the same colour connector
I have seem a similar set up on the mk2 machines of various types but I cannot say its the same board
They was originally sold as a pair of boards but to reduce the cost as some people have asked me to sell these in singles as they only want to balance one side of their units I am selling as one
I do not think the kit included anything else, you will get one XLR panel, one PCB for that and screws for one side of your unit, if you need two you will need to order two of these.