Did you put the two plugs behind the cam plate?
I have had many 340's and none have had plugs behind the cam plate. I don't know when they started using them, at one time I was going to put them in because the owner wanted them in but the plug was so long that it would cover up the oil galley hole going to the right lifter galley from the front main, so long as the plate is flat you don't need them.