Is your 84 equipped with CFI? If it is, you'll definitely want to either go to SEFI with MAF or a four barrel carburetor.
The 5.0 is capable of handling about 550 horsepower before coming apart with stock internals. Ford Racing only recommends 400 horsepower before going to an after market block.
Just about any Ford transmission is capable of handling 300 horsepower. If you have an automatic transmission you'll want to invest in the proper converter, a shift kit, and a new transmission cooler.
The 7.5" (if you don't have the 8.8")rear axle's life would be short lived at 300 horsepower. The 8.8 is capable of handling 300 horse easily. You may want to install lower gears, limited slip, and disc brake to handle the added power.
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93 Thunderbird 5.0 HO
89 Firebird L03
95 F150 XL
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