Gary, very hard to be sure from the photo, but it looks to me like the newer ('56-'62) style solid lifter. Best way to tell is to pull one, so you can verify if it has the movable internal plunger of a hydraulic lifter or not.
Photo I've attached is of a Melling JB-874 solid lifter, replacement for the OE lifters used from '56 onward, which looks pretty much like your photo. The longer "milkcan" solid lifters like Buoymaker posted were used through '55, with a shorter pushrod. For the solid lifters after '55 (or the hydraulic lifters from '53 onward), the OE pushrod length is listed as 11-13/32".
