273 hydraulic cam/pushrod/adjustable rocker combination.

hope they are crane
if they are coverted from the interference thread stock ones then be sure the cast iron where the jamb nut sits is flat- use a big file
do the mid lift test
at half lift see if the top of the valve tip lines up with the center of the shaft
you can use the retainer and a machinist ruler to eyball it
usually not a problem unless you have long valves or a really high lift cam (or both) but...
if that checks out you do not need to relocate your shafts
then open up the push rod holes
some high lift applications we use cups on the adjusters and ball and ball pushrods - not necessary with your lift
that cam duration is at SAE= .006 at the valve or .004 at the cam with 1.5 rockers
more like a 280 @.006 cam
Factory rated that cam at what - the stock 340 cam was 268 and the 4 speed cam what 272? I forget but the equivalent of measuring at around .008
It's not a "290" class cam