And while you're on the LPGear website, they have a nice deal on the Audio Technica AT-95E cartridge, which will sound very nice on this unit. Or, you could spend a bit more on an AT-120, or even an AT-440MLa. That will set you up very nicely.
The silver headshell would look more at home on the 516 than the black one, IMO. And ditto on what Hakaplan said about ordering the OEM belt -- that's your best bet, although since the 516 has a pitch control and strobe, it's not as crucial as a TT without one.
When your package arrives, get a small machinist's ruler like this one, most hardware stores have them:
Then set the little right angle thingy to 1 59/64 inches strong, which is the equivalent of 49 mm. Rest the right angle against the gasket on the headshell and mount the cartridge square to the sides of the headshell with the diamond tip even with the very end of the rule. This is the spec for Pioneer arms.
Most Audio Technica (AT) cartridges are color coded, so just connect the headshell wires red-green-blue-white to the appropriate pins after mounting, connect headshell to tonearm and rock n roll.