No, the Tampa is nothing like a Mustang. It is primarily based on the Dodge Dart Demon.
sh*t took me forever to get the images right lol.
i already know this but i'm talking about R* not what you and me think it is. you know by fact R* sometimes doesn't care about logic since apparently the Huayra is a Lamborghini to their eyes and a charger is a chevy instead of a bravado. but judging by that Boss 302 livery there is no doubt R* designed it with mustang in mind.
I could care less what they call it or what brand they make it. As long as it is a classic Mustang. I have to disagree though, I don't think any of the Tampa is inspired by the Boss. Not even the stripes. I think it was pretty clear it is supposed to be based on a Dart and not a Mustang. Literally without the side stripes it looks almost identical to the real Demon.