There's two types of lifter construction,the material that is,chilled iron and hardenable iron.Chilled iron lifters are meant for use only on steel billet cams,hardenable iron is for cast cams.
All the milk bottle lifters I've seen are chilled iron.These lifters are heat treated on the bottoms only,the other style are hard on the whole lifter body.A fine file drawn across the lifter side will tell you the lifter type,the file will cut the chilled iron lifter.Maybe some milk bottle style lifters aren't chilled iron?
Most cam grinders say using chilled iron lifters on a cast cam will invite premature lobe wear.A few say it doesn't matter.
I believe the Bulldog cams are cast iron like the almost all cams available for these old engines.
