p.1 #3 · Short/no center column option for old Gitzo series 3 tripod?
The quick and dirty (and cheap) solution is to use a plumber's pipe cutter on the center column, for a clean and square cut. This is what I did on an old 1-series Gitzo aluminum column:
p.1 #4 · Short/no center column option for old Gitzo series 3 tripod?
Ya, if nothing else works out I will probably resort to a cutting tool myself. I had no idea about the ground level kit, I will confirm if that will work.
Thanks again for the link to the leg spikes, I will contact Manfrotto tomorrow. Too bad Gitzo can't be called here in the US (at least as per their US website, all I can do is email to their Italy HQ).
p.1 #7 · Short/no center column option for old Gitzo series 3 tripod?
I use the same tripod, but merged mine with modern carbon legs. I just love that smaller diameter head casting, and I use a standard Gitzo short center column pretty much permanently held in by the lower collet. Looks like your first pic is very close to that already. I've done this to two Gitzos so far and they are my main tripods, used that way for years.
But to answer your main question, yes, the series 2 short column (about 1.25" diameter) will work fine. I got mine for about $30 on ebay. Sorry I have no ics of my pod, but will make some this weekend.
p.1 #8 · Short/no center column option for old Gitzo series 3 tripod?
That would be much appreciated, although I will admit I am contemplating selling this and going Carbon Fiber. This thing is a massive beast, and the B&H student discounts on Induro CF tripods are very appealing.