Those are some old axles.
I don't think Henrys has made flanged axles for at least 20 years !
I've ocasionaly had 4WD customers bring components from them since they are still in business.
http://henrysmachine.com/ call them and ask what angle spline they are.
Most likely they are 30deg like Strange. M-W is 45 deg.
Just a safety warning, years ago Henrys, Geise,and probably others made their axles 2 piece, welding the flange to the shaft and then heat treating.
OK for 300hp and 7" slicks,but today ?