Using
profootballreference.com's Career Approximate Value metric, the highest scoring Chiefs are:
Tony Gonzalez - 172* (26th all time)
Joe Montana - 164** (37th)
Bobby Bell - 149 (69th)
Len Dawson - 147 (76th)
Mike Webster - 143*** (90th)
Marcus Allen - 142**** (93rd)
Johnny Robinson - 140 (100th)
Buck Buchanan - 138 (111th)
Dave Krieg - 138***** (111th)
Will Shields - 133 (139th)
Willie Roaf - 133****** (139th)
Derrick Thomas - 131 (152nd)
Jim Tyrer - 130******* (160th)
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* 128 AV pts during Gonzales' 12 years with KC
** 18 AV pts during Montana's 2 years with KC
*** 9 AV pts during Webster's 2 years with KC
**** 36 AV pts during Allen's 5 years with KC
***** 17 AV pts during Krieg's 2 years with KC
****** 52 AV pts during Roaf's 4 years with KC
******* 128 AV pts during Tyrer's 13 years with KC (and Dallas Texans)
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So if you only count CAV in a Chief's uniform, the leaderboard looks like this:
1. Bobby Bell
2. Len Dawson
3. Johnny Robinson
4. Buck Buchanan
5. Will Shields
6. Derrick Thomas
7t. Tony Gonzalez
7t. Jim Tyrer