For the pickup cover I think basically imagine the split pickup occupied a large rectangle drawn around the two pickups. Now imagine the bottom of the left hand pickup was the middle, and the top of the right hand pickup basically shows the mid point of the whole pickup area. Now measure the width of the split pickup. Measure the width of the ashtray. Subtract the width of the pickup from the ashtray, half the remainder and you know how far out along the pickup midpoint to drill your holes.
Drill the pickguard in isolation, DO NOT drill the wood until you know you are right on with the pickguard.
