I am installing a complete 1978 Pinto power train in my 31 Model A pickup.  To do so will require narrowing the rear axle housing by 2.25"  (1.625" on each end) and shortening the splined end of each axle shaft by the same amount.  As a matter of choice, I prefer to modify the superior Pinto rear end as opposed to altering the noisy old Model A banjo axle.  I don't want to disturb the perfectly operating Pinto differential and carrier assembly, by dissembling the unit to measure the length of the spider gear splines. Can anyone provide me with the spline design dimensions for this 1.625'x28 assembly?   I have professional machining and welding capability to make the mods, but don't want to assume anything about these modifications without first doing do-diligent research. 
Thank you, in advance, for any assistance you can provide. 1olfrdanut