I'm wanting to drop a 5.0 into my 99 Mustang (3.8) I found one article about doing a V6 to V8 swap from 94 to 98 Mustangs. .. but the 5.0 I'm looking at came out of an 89. .. it's fuel injected and has a computer. Since there's a 10 year difference would this be more trouble than it's worth? I'll take all the help I can get!
Thanks!!

 

This is a very cost inefficient swap and you'll hate yourself for starting it.

I'd suggest you keep an open mind (we're not bashing you but you did ask for the good/bad idea bit) while the boys tell you why it's a bad idea and how doing a 4.6 or 5.4 swap will make you happy without breaking the bank quite so badly.

Honestly, I'd recommend you sell the v6 and buy an 87-93 GT or 5.0 LX and go from there. You can pick up a whole car for under a grand in most places and then you'll not have to buy the THOUSANDS AND THOUSANDS of dollars in parts to make the 5.0 (or even a 4.6/5.4) work in your 99. Besides, fox bodies are way lighter.