A body BBP axle length for 8 3/4"

Great info thanks everyone. This is clearing things up for me. I have a 8 3/4 rear end for a 69 a body and would like to convert it to BBP. I have some BBP axles that are long enough and large enough in diameter to be cut down to proper length and resplined. I also have a 8 1/4" donor for the brake hardware. I'm unsure what proper length is since the bbp axles are off set more between the bearing flange and the wheel side of the flange. If the chart on the sticky and my math are correct I think the axle will need to be 11/32" longer than a SBP axle. This is how I came up with 11/32.
According to the chart all A body housings are 52 5/8" wide. SBP rears measure 57 1/8" drum to drum. BBP rears measure 57 13/16". A difference of 11/16" total. One axle would be 1/2" the total or 11/32". So if a SBP axle is 27 11/16" then would my axle need to be 11/32" longer or 28 1/32"?
All that said I did not know there was an axle you could buy with BBP that you could use with SBP drums that is the correct offset between the bearing and wheel flange. Sounds like you just slot or re drill the drum to fit? Yukon brand? Does anyone know the part number for this axle? This might be an option instead getting axles resplined. Thanks everyone for the help.