If it’s what you want, and you got the bucks, get it. Just to let you know, NADA has a 351 Mach 1 in “high retail” with A/C for $21,500
Like Packrat said, the “boss 351” description is troubling so check to see if it’s a mistake or if the seller really thinks it’s a 69 boss 351 Mach 1...