[lust4speed]

With the engine upside down on the stand, pan removed, and the main bearing caps removed, the crank can be lifted up about 5/8" before the rods bind in the block. Cherry picker and a strap will hold the crank up. Not my favorite method because it's difficult to fully clean the groove and the anti-rotation holes and get the new rope seal in place. Also a problem with the Viton seals getting the holes cleaned and filled with a little silicone so oil doesn't get past the seal.

Method #2 is to remove all rod caps and tap the piston/rod assemblies down to resting on the heads that are still in place. Requires just a little manipulation pulling the crank since the rods that are on the journals close to the block want to hang up a little. Turning the crank while pulling it out will get around this. Once the crank is out you are back to dealing with things just like a new installation.

Getting the crank back in requires carefully pulling up the piston assemblies and setting them on the rod journals as you finesse the crank back in place. I've pulled three engines of club members and did the repair as described above. The crank pull is more work but gives full room for getting the seal in correctly.

Also, as Ken said above, take a good look at seal position when you pull off #5 cap and see if the serrations might have been the problem. if it is, well you will have the crank out and can have the serrations smoothed out at the local machine shop before putting things back together.

Photo is from 2011 of a friends '72 455 HO engine. Rope seal back in and as far as I know it's still not leaking. You have to look close to see the rods.