I've changed lots of upper rope seals with the transmission still insttalled. It only takes a few thousandths of movement to free up the seal so it can be rolled out of the block. The tool kit with the long-handled puller with the screw end makes a huge difference, as it gives you enough room to get a good pull on the seal. Once the puller is screwed into the seal, a thin-bladed screwdriver inserted between the seal and the block makes a handy pry bar to help get the seal moving. If you need a little extra movement, loosening the transmission-to-bellhousing bolts might help, but I've never needed to do that.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!