Yep I did the same conversion, 35 spline aftermarket axles/side gears/clutch kit. Cass was very helpful and reasonable on cost.

AFAIK the axles will also fit into a 35 spline spool without a problem, but if you use the spool you have to use green bearings not the oe tapered rollers.

The increased OD of the 35 spline axle is past the splined area...oe 23 spline necks down past the splines, 35 spline aftermarket is about the same thickness all the way down to the wheel flange.