slant six lifter swap

The lifter pulling tools (that I am used to) ususally are made to pull a hydraulic lifter by grabbing into the groove inside the top of the lifter for the retainer clip. There is no such groove in the top of the /6 mech lifter.

So you are left with grabbing the upper vertical lip of the lifter. The issue is that these are barbell shaped with a narrowed 'waist' in the middle of the lifter body; they do not move up and down enough to fully wipe the lifter bore in the area of the waist and so can build up a ring of hard varnish halfway down the inside of the lifter bores, and this catches the lower part of the lifter body.

Be prepared with some narrow jawed vice grips or hemostats to carefully grab the upper lip, and some carburetor gum cutter to soak down around the lifters to help soften the varnish if need be.

(FYI, my horrendously varnished engine required that I disassemble the engine, flip it over on the stand and drive all the lifters out with a hard maple dowel and hammer! But that was the worst varnished engine by far I have ever had. I doubt you will have that experience... at least I hope not!)