The rockers you have are superior to the hydraulic style. Stay with them and get push rods . You will be able to adjust your hydraulic lifter preload with the adjusters rather then using shims under the shafts. And most of these new lifters need adjustment and do not work with the stamped steel rockers. Don't let anyone con you out of your rockers.
Also the stamped steel rockers used on a standard 340 Hydraulic cams are not the same as a 318 or 360. Sure they are the same Part number . But they are clearanced for the spring retainers. That work will cost you more then Push rods themselves.
I have many rockers like you have and you'll never see me sell any. I keep them and sell the stamped steel cheap. Nothing is better then the iron non roller rockers for endurance on the street. No needles bearings or rollers to fall out and destroy an engine