I'm pretty sure the old ford small block is smaller than an sbc. The big problem with using one is finding a rear sump oil system for it. Idk if the fox body pan would have enough clearance
I don't remember what the reason was but a buddy with a 5.0 in a CJ-7 had told me it was harder to mount than a SBC. But he had one in his and it was a sweet rig.