in too deep: trying to go BBP on a 68 barracuda and its going.. poorly.

All 8 3/4” axles are 30 spline, so your reference to the 10 spline count is in the yoke, which has no bearing on your axle change. I doubt it’s a 10 spline yoke anyway on a 741 case. Changing to BBP axles is as easy as buying the axles with the correct offset to use BBP 10” brakes. What you use for bearings on the axles is up to you, I believe you can buy them with tapered bearings and use your old races, or with green bearings. Your choice. When buying the brakes, try to get a complete set from your donor source, as there are different shoe widths, and you need the corresponding backing plates for the width your are buying. You’ll get it, just take a couple shots of patience before you head back out to the garage.