This is good advice, to which I'll add a bit more. I've done similar trips a number of times over the past couple of years.
As Squarebutt says, take the MA 'pike to I 84 down through CT and into New York State. This will keep you out of NYC and NJ. As long as your firearms are locked up securely, you should have no problem even if you are stopped. Just don't mention that you have firearms and you should be fine.
If you're stopped, say as little as possible, don't allow a search.
Take I-81 as far south as you can. Check the counties that you are passing through in PA. LTCs in PA are issued by the county sheriffs and they determine if they will issue to non county residents. Find a county that does issue along your route and stop in to get a LTC. It took me 10 minutes in Berks County.
If you have smart phone or iPhone, download the app "Legal Heat". It's a good guide to reciprocity and the laws of the individual states.
Unlike MA, most states don't require a permit or license for mere possession. So, as long as you keep your stuff locked up, you should be fine. Unfortunately, MA, NY, and NJ do require permits for mere possession.
hangunlaw.us is a good source of information a well.