Hi and welcome,
Are you looking for a drop-in replacement, or prepared to modify your deck somewhat? Either way you will probably have to make an armboard to cover the original hole , but if the mounting distance is similar you might not have to drill through the plinth or not as much.
For a 103 cartridge I'd recommend looking into a Jelco 750d (around 5 - $600). It's a heavier arm with fluid damping and your 103 will like it better. There's a less expensive 370H sold on fleabey, should do the job nicely. With that one you'll have to terminate the wires yourself, we'll help you figure it out.
Mounting distance (spindle to mounting hole center) has to be fairly accurate, but if you can do basic carpentry it's not that hard.
neo
