Mustangs ARE fun...when they run, and Merlin's is ****in' possessed. It makes all the right sounds and it runs strong but let's face it, it's an older car with a lot of miles that hasn't had any TLC until he got hold of it. Mine's creeping up on 140k but the difference is the last 100k of it have been mine, I *know* what its history is and what's been done to it and how it's been treated.
I know what I'd do if I were Hiatt (ahem), which is sell it, take the proceeds and put them straight into a clean, unmolested 5.0 with lower miles and go from there. You could have one running 13's without even cracking the heads off. Yeah, you gotta pay to play...SORT OF. Those things are just stupid cheap to mess around with compared to just about anything out there. Sure you can go faster easier but you have to start with something more expensive in the first place.
Sure, you want to go REALLY fast or look REALLY nice doing it, it's gonna cost bigger bucks. No two ways around it. Really fast, really good looking or cheap, pick any two. But you could (and I would) find a pretty damn clean, reliable '90-93 that's stock or close to it for $4,500-5,000 and have it running 13's for maybe $1,000-$1500 more,and not necessarily all at once. But in the meantime if you do your shopping right, you have a daily driver you can depend on. Do the right shopping on intake and exhaust parts, some decent gears, throw on a set of DR's and a shifter, and laugh all the way to and from the track.
But that's just me
BTW I just put a smaller blower pulley on the GTP and removed an exhaust restriction and with the CAI she's only 1-2 lenghts back from me at 80. But that car took twice the initial outlay and then some. Still a bargain but not like a cheap-as-nuts used 5.0.