273-318 rocker shaft differences
63, This is possiable that the lifters are going down, most stock lifters do go down to help with start up. (less lift and less duration) But after the engine has been run and up to temp. that the lifters should hold the oil, if this occurs after the engine has been run then the lifters are more than likely bad.
As for the shafts there are a number of places that you can get them, but check with mopar 1st, then if you still can't get them let me know and I'll get them for you and send them to you at what they charge me and shipping, they generally run $90-100 but they are better than the stock shafts and will support both rockers setups. Summit, Jegs, Doug Herbert, Harland Sharpe all offer shafts but this is your choosing, pick the best and go with it.
BJR Racing