Early 273 Oiling Questions

you have oiling from the cam through the cam bearing up through both sides of the valley to the block to the LA heads ( not magnums)
The early LA had solid lifters with no oil through the pushrods and a small cup for a small ball pushrod- very obsolete
later lifters had a bigger cup for a larger pushrod ball- use the later parts no mix and match- toss the old stuff it did not wear well which is why Chrysler changed
Now almost all lifters for SBM FT or HYD use the AMC/Magnum style lifters with the capabality of oil through the puhrods- use these
no reason to search out the older non oil through the pushrod FT or HFT lifters
I like to have the extra oil to the rocker adjusters anyway especailly with more than stock spring pressure
you have the adjustable rockers use them
if needed send them or exchange with Rocker Arm Specialists for brass bushings and new adjusters- get the cup type instead of the ball type then ball and ball pushrods with the oil holes
check your shafts for wear and gauling and reface the valve stem pad on the rocker

BVVC if thinking of roller tip rockers- to work right they need a kit from B3Racingindustries
go there and read the 4 tech articles