All 9's can be shortened. The spline count depends on the spool carrier and bearings....someone correct me if im saying this wrong, im no expert. All 9" housings can be shortened and run any spline.

The two types of 9" are small bearing housing and large bearing housings. The large bearing housings require a large bearing brake backing plate, whereas the 9" small bearing housing will utilize 8" brak e backing plates. making the swap easier.

Im building my 9" right now, I found a 69 mustang housing and I relocated the spring perches and put in 31 spline mosiers, with a 31 spine posi carrier. Good to go.

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'69 Ford Torino Formal Roof 302
Live for this!