How reliable is a 5.0

[vtechatch]

I am sick of my Civic.I spent alot on it last winter when I really wanted an 87-93 Stang.
Well now I can sell it for about 7000 and I want a good Fox body stang.
I like the looks of the GT,I really like the 86 Mustang GT,But I like the 87 up a little better.

Ok what kind of problems show up on this car?

Anything expensive?

What should I expect to run on a stock used 87-93 GT 5 speed?

My Civic ran a 14.7 with just the motor swap.I havent ran It with all my mods but Im sure I didnt shave a second off for alot of cash spent.

Also I know it asking alot,but what would the above said Mustang run with good headers,exhaust,Intake.I plan on getting those parts right off the bat.
Thanks
Dan