Correct me if I'm wrong but wouldn't it be ashame not to pop out the pisons since you have the heads off and will have the pan off as well? It seems that most the hard work is done at that point. I once rebuilt a 4.5L MB engine with 150k miles that was burning lots of oil (1qt/500miles). The oil scraper (bottom) rings were completely caked and allowed oil from the bottom end to work up into the combustion port. Changing the rings fixed that problem and 100k miles later it still isn't burning oil between oil changes. Didn't even need a rebore (just a light honing). Of course if you are not going to keep the car you might as well not even open the oil pan. If you are opening it up then you must be planning on keeping it. If you take out the pistons you'll need a ridge reamer else you'll destroy the pistons. Might as well replace the rod bearings while you're there.

Good luck

__________________
1972 450SL
1982 300D Turbo