Mint 400 sprocket size?

[crash carden]

  Hello, can anyone help me out with what sprocket size both front and rear would be best suited for a early 1975 Mint 400? I ride woods/enduro and harescrambles. The bike has the enduro pipe w/the chrome tip,and a Gem reed valve on a bing carb.The bike needs new sprockets and I don't want to buy the wrong size. Also should I buy  520 or 530 size? I have never riden a Mint 400 so I have no idea of what set up would be best for me or the bike. Thanks for any help,
                              Crash Carden

[Merlin]

...........my big Penton works well with 14/52,low gear is still low enough to count the power pulses just above a stop and top gear enough to keep your top speed need happy,as for the 520 vs 530 I have a fair sized stable so 520 is it(common spares as well as selection),if you have a small fleet 530 may be for you...........