273 adjustable rockers on 360, very little oil to springs

Are the bolt holes in the shims the same diameter as the oiling hole on the head?
This is GOOD observation.... if the OP has shims UNDER the shafts. The hole in the underside of each shaft at the 2nd hole from the left is larger, to allow full flow from the rocker stand. A small shim hole at that location would restrict flow. This area is the controlling flow restriction in the stock oiling path to the rockers (after the 'cam interruptor').