I looked in the tech wiki, The regular cam for the USA delivered A15's ex B310 is the:

Part Number
13001-H5700

@
?

Ex. Dur
256

In. Dur
248

In. Open
14

In. Close
54

Ex. Close
20

Ex. Open
56

Lift (in)
0.331

going off those numbers the calculated ideal primary length to the collector is estimated at 37.12 inches. [for peak power at 5000 RPM]. The length gets shorter as the RPM /peak power increases

The kicker is though, the reference material doesn't specific if the numbers quoted for the timing event are "advertised" or at "50 Thou"