Ordered a new cam today for the W2 408

A few things can cause bucking/surging. Too much timing, lean mixture.
Widening the LSA is the wrong way to reduce overlap; you reduce duration & keep the correct LSA.

D. Vizard has a veeeeeeeeeeeeery good you tube on this titled Fords 303 cams; sorry, do not know to link it, maybe somebody can.