5k isn't going to buy a nice driver, only an entry price for a driver..to get a driver, ready to go, you'll need to spend closer to 8-10k. a '74 is a good car, as far as the mid-year cars go..they have the more-desireable exhaust, the 7:31 ring and pinion (quicker off the start), and don't have thermal reactors, which contributed the most to the mid-year car problem of head studs pulling out of the softer magnesium case (the later 3.0 liter motor is aluminum). all that said, rust is the big question here. all the above comments are true..rust could be a major deal-breaker..you have to check that out or find someone qualified who can tell you what it would take to make the car right in terms of rust..maybe it can be..it's always nice to see someone 'save' a mid year car (speaking as an owner of one). the vibration could be something as simple as tire pressure or unbalanced tires..you won't know unless you check it out. a ppi is mandatory here. you might find the problems can be addressed and might be able to get the car for a really low price if you just really want to get into a 911. the owner might let it go for between 3-4k, but be prepared to double that in no time. personally, i hope it can work out and you can put some love into a mid-year car that needs it. i'm wearing a flame suit, so i'm cool..flame on, bad boys..
ryan