If it is lean surging at a steady higher cruise RPM I would increase the jetting a small amount(.002 to no more than .004) first twocents I would also work on the distributor later to set the curve up so you have between 10 to 18 BTDC at idle and no more than 36 total revved up wth all the mechancal advance kicked in up twocents IHTHs

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)