I'm working on a 69 custom S and I rant into a snag when replacing the rear axle bearings. I purchased new axle shafts and new bearings while I'm installing rear disc brakes on my car. I didn't take a measurement when pressed off the old bearings off so when I pressed the new bearings on the new axle shafts I pressed them on as far as they would go which in looking at it now was probably wrong. When I bolt the retainer plate to the axle housing then try and assemble the brakes the new rotor hits the caliper bracket. Does any body know what the stock distance from the outer axle bearing is to axle flange?
Will be out tomorrow and measure a stock axle. Your '69 Custom S, the axle uses a sealed axle being with the internal seal up in the axle housing? That is the most common axle in a '69. I've only ran across a few tapered bearing axle '69 Pontiacs, and they were all late season '69 Firebirds.
Bearing wise, the RW507C axle bearing was used from '64-69, the RW507C is the same OD and same internal diameter as its successor, the tapered axle bearing A9. The axles for an A9 bearing are machined slightly different and have a smooth surface right outboard of the step in the axle so the external seal (National 712146) will have a smooth area to ride on.
typical aftermarket rear disc brake kits require spacing the caliper bracket out some from the r/e housing flange, this is so the loaded caliper will line up with the rotor. Most such kits are made for cclip rearends like the Chebby 10 bolt or 12 bolt.
When installing on bolt-in axle rearends, the caliper mounting plate must have a bore large enough, so that a custom spacer that butts up against the axle bearing or axle bearing/external seal and extends out through the thickness of the caliper bracket, then the axle retainer clamps up against this spacer. The spacer limits axle movement in and out, and allows for the bolt in axle to be slid out of the assembled rearend with rear caliper brackets mounted intact on the rearend housing.
First adapted '79-81 T/A rear discs on a 12 bolt Chevelle, a '69 Firebird housing and several 8.5 Abody rears in the '90's. Over the last 10 years, have pulled and sold numerous S10 rear disc pieces to adapt onto cclip and bolt in axle 8.5 rears. Either style of rear disc brackets and calipers used in a swap presents a few challenges and will often require a certain size spacer.
Budget (chinese) axles...would really help to have the dimensions of the replacement axles you have. Whatever set-up you are using, the axle bearing should have indeed be fully seated on the axle.