yes it is a 2 piece seal. it just funny that all the other manuals i have say to just pull the pan and cap, and this particular manual (but only for the 351m) says i have to pull flywheel, loosen all main caps and slightly lift the crank to change it out, but only for the 351m.
i'm going to give it a go this weekend anyway and see if it can be done, i think it can. even if i have to pull the engine, it only takes an hour or so with a couple of friends, beer, pizza....mmmmm pizza.....