Yup, it will fit. The 9" you will probably have to modify to be the right length and have the right attachment points to bolt it in, so it may be better to sell that and get an 8.8 that will bolt right up in the bird. Otherwise, it should be pretty straight-forward, especially since your car is carbed already, so the only thing you will have to figure out is motor and trans mounts.
-91 Cougar LS, coming soon, complete overhaul with a 427" Windsor.
-90 XR7 5-speed black on black w/sunroof, MP2, coated rotors, double intercooler, 15%OD, ported heads, comp stage 1 cam, 85mm TB, 90MM LMAF, 80# injectors, and ported big valve heads
-98 Mark VIII LSC, Procharger P600b, TR3650 swap and 3.73s.
-90 SC Automatic rustbucket winter beater
-97 Tbird Sport 4.6 Nice weather daily driver
-"Your buddy Mike is INSANE!" -ClintD's dad