If you have it bored at 4 thou and it hasn't nipped up along the way (a miracle), then I would be looking elsewhere.
I am running double that clearance (same mileage), with no problems - so I doubt it's blow by.
Were the rings 120 degrees apart at assembly?
Does the motor burn oil?
I'm a bit intrigued by oil coming from head bolts.. Both or just one?
The first place I'd look would be for good valve seating - riding tappets, bent valve, bad seats, worn guides.
The second would be around the top end for cracks - and then maybe broken rings.
'51,'56 Squares, '48 VH, '27 Model C, R67/2, Mk IV Le Mans, '06 Super Duke and Ariel projects.