....Two points:

1) If you do a search on YouTube - failing there, try Google, natch - you should still find some of the Saturn V Status Reports that were filmed for admin briefing purposes. One of them goes into a little bit of detail about the gore process, but as it was explained to me years ago, in a nutshell North American created a concave hemispherical mold, placed the sheet metal over a water tank with an explosive charge at the bottom, set the mold on top of the sheet, clamped it all down tight, lit the fuse, and BLAMMO, up goes the non-compressable H2O against the sheet, up against the mold, and voila! "Instant" fuel tank top/bottom!

2) Funny you should mention the S1B on top of the S-1C stage. I was thinking about a post I'd made here and on rec.models.scale about "The Ultimate NASA Booster", in which the S-1C was topped with an S-II, which in turn was topped with an S1B first stage, then an S-IVB, then a pair of Titan IIs - both stages, mind you! - with an adapter stage, topped with an Atlas with a Redstone on top.
All to put a Vanguard into LEO as a tribute to government spending policies that allow for $15,000 ball peen hammers and $20,000 toilet seats...:P

Oh yeah, I took some spankings over the issues of altitude and "fire in the hole!" requirements, but you gotta admit that the whole stack would have looked pretty wild with a good paint job...

OM