Here's my two cents- I've done it both ways, and no longer even attempt to pull the pan with the engine in the car. I would maybe make an exception to my little personal rule to change a rear main seal on a car I wanted to sell, but that's about it. In my opinion, it may take a little longer to pull the engine, but it can be far less frustrating. Why do you need to pull the pan??? The more work you want to do down there, the better off you are to pull the whole engine. If you are doing it to replace the pan for some reason, I can tell you I've had bad luck with aftermarket "stock looking" pans going back on after the original one comes off. The transition area going down into the sump is usually a gentler radius on aftermarket versions, and that's the area I've found to get in the way.
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Steve
72 Chevelle SS402/4sp