It's been awhile since I've broke them out, but listening to the Jan. and May Boston '69 shows, after the very first listen, I immediately thought it was more than likely one of the May shows if a 4-hour marathon occured. You can listen to the excitement build in the crowd as the show goes on. There's one moment (during Bonzo's solo maybe? can't recall precisely) that you can almost hear an actual "gasp" go through the crowd....in all my years of listening to boots from all sorts of bands, I don't ever recall hearing something like that in a crowd.
Makes me want to throw it in and give it another listen.