your oil pump should very easily provide 2 gallons or more of oil volume per minute even at lower rpm idle speeds ,
those oil spray holes drilled in the front oil gallery, passages are not your main issue.
the most likely problem, (but certainly not the only possibility)
is the oil pump pick-up is being restricted by being too close to the oil pan floor
on most engines this MUST be checked carefully, but most people fail to do so.
they assume if the pan bolts on, its going to be fine
your oil pump may be loose , not secure to the rear main cap,
and certainly having two over size holes drilled in the gallery plugs is not ideal.
the oil pump pick-up may not have the correct clearance,
you may have the rockers adjusted too tightly,
or the distributor lower band diameter is significantly smaller than the block,
allowing a significant loss of oil pressure reaching the oil passages.
certainly having the 1/16" holes that are 4 times the suggested cross sectional area,
and having two, rather than the suggested single .031 hole, does not help
why not start by doing a couple quick tests,
(1) add 1 quart of oil too the pan, and back the rockers off one full turn each,
if the rockers are too tight oil flow volume from the push rods is greatly restricted
http://garage.grumpysperformance.com/index.php?threads/correctly-adjusting-valves.196/
(yeah it might be noisy but it won,t hurt anything during a quick test)
if you see a significant improvement in oil flow the rocker adjustment was not correct
(very COMMON)
now spin the engine over with the starter with the coil wire removed ,
if you don,t see oil exiting the rockers in 60 seconds ,
you really need to check that oil pan to oil pump pick-up clearance.
if clearance issue checked with clay and a temp re-install on the oil pan to check clearance, checks ok,
you likely need to swap to a new oil filter , fill the new oil filter before its installed with oil and repeat, (try WIX or PUREALATOR) and
if the issue does not improve you likely have an oil plug missing or incorrectly installed some place.
http://garage.grumpysperformance.co...ilter-you-sellect-does-make-a-differance.117/
I really wish I could stop by all of the guys who, post questions,
about having problems, as most are simply resolved with few tests
while your checking put some modeling clay under both pick-ups and see the effective clearance difference then see if the old pump clears the problem,
in an ideal world the pick-up to pan floor clearance is a minimum of 3/8" and 1/2" is ideal
every time the oil pump completes a revolution a predictable volume of oil is forced up the pump into the oil passages, in the block,
even at idle or about 700-750 rpm, thats several gallons a minute.
you can restrict the oil flow into the pump , rather easily,if the oil pump pick-up, too oil pump floor clearance, won,t allow oil to enter the pump due to very limited access,
as its not pressurized, once its flowing thru the oil passages, pressure is a measure of the resistance to flow through the clearances in the bearings and clearances.
If oil fails to exit the push rods its obviously either exiting else ware or not able to flow into the push rods from the lifters and lifter gallery.
be sure not to insert oil passage plugs into oil gallery passages too deeply
threading the oil passage plugs increases durability and I generally suggest drilling an oil pray jet hole thats .031-.035 in the pass side oil pass plug, THE ONE AS YET UN THREADED IN THE PICTURE ABOVE
PLEASE post the results you get during testing,
and info you find,
as its sure to help others in the future
http://garage.grumpysperformance.com/index.php?threads/installing-an-oil-pump-pick-up-tube.1800/
http://garage.grumpysperformance.com/index.php?threads/oil-system-mods-that-help.2187/
http://garage.grumpysperformance.com/index.php?threads/bbc-gen-vi-no-oil-pressure.14987/#post-84634
http://garage.grumpysperformance.com/index.php?threads/not-getting-oil-to-rockers.4537/