Once in a while a 744 is brought in for that route, although I think it's rare. When I flew BOS-LHR flt 238 in early March, I was on a 744, much to my surprise. Coming back, however, I was on a 742, new livery (Paithani tail I think) with no PTVs. If you end up on a 742, try to get a seat in the Upper Deck. The 742s are still world traveller seating up there, and it's much more mellowed out and away from the masses. I did that coming back to Boston and it was great.