Yes, the front engine crossmember is different than the 4 cylinder/V8 crossmember. I had an '83 Zephyr with the 3.3L and i looked into putting a 5.0 into it. You will need to get that as well as a double hump transmission crossmember for the dual exhaust if you don't have one already. Good luck on your project!
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'84 Mustang 5.0 LX
My car