I put a 3.8 from a 98 mustang in my tbird. Minimal work required. Changed exhaust manifolds, a few sensors, and wiring harness. Started right up and no Codes. I noticed in my search that mustang engines were alot cheaper than tbird engines. The one I bought had 70k miles and cost me $350.00. The same yard wanted $650 for one out of a 96 Tbird. I found it on car-part.com.
My nest: 93 White 5.0-- 94 Green 4.6-- 96 Green 3.8 --97 Red 4.6 limited edition---95 SC 5 speed