Not that simple....... the early disco's used imperial axles...a10 spline with fat drive flange ends..... the late 200's and very early 300's from what i can gather used a metric 10 spline.... with flat ends.......... and the later 300's used a metric 24 pline axle..... again, flat ends............ the casting numbers for BOTH the flat 10 AND 24 splines is the same............ i have both in my garage!
so, if you have flat ends, you simply HAVE to pull a shaft to check, however, IF you have the three pronged rubber coupling on the rear of the prop...... it's 99% bound to be a 24 spline one.....
