on the inside edge of where the bearing sits in the axle case.. I drilled it at about 45 degrees relative to the leaf spring so I'd have fairly easy access.
Are the bearings an open bearing or a sealed bearing?
I placed the zerk on the diff side of the bearing, so if I go hog wild it'll end up going past the inner seal into the axle tube, where it'll have no ill effects. I only inject grease every 6K miles or so, and then only 3 pumps of the grease gun.
Grease is a lubricating oil with a soap thickener designed to hold the lubricant and prevent run off of the oil. Depending on the particular gear oil in the rear end and the grease being used and the inner seal starts leaking it's possible the thickener could not be compatible with the gear oil. There are many blends of gear oil and many blends of grease so you need to ask if the products you want to use are compatible.
It could be an issue due to the changes made when blending lubes since these cars were built. After almost 40 years of being in the lube business and seeing the changes that have been made in lubes I've learned to question compatibility. It's all up to the owner concerning what he does.
I do that as well
Sunbeam Talbot 90, made from 1950-57... My father has owned them since the late 50's... probably how I became a British car wrench!