I guess that the choice between all these excellent suggestions is going to hang on the tonality you want. Do you want the 'pushed' look or a softer tonality? I'd go for a film/dev combination that gives inherently high graininess without a push - so Ian Grant's suggestion of D 163 (or maybe Ilford PQ Universal) and Ole's FX-2 stand process with Delta 3200 (not so much as push, more a true speed increase) would be my choices. Delta 3200 is the grainiest film I've used recently. When I tested it with Barry Thornton's DiXactol I got very high graininess (objectionably overwhelming, in my opinion) and extreme overexposure latitude, with a speed of around 1000 based on shadow detail.
Nobody's mentioned overexposure: just one more way of getting higher graininess with silver-image negative film, and another reason to prefer a non-push process.
Another way that springs to mind because I tried it: use outdated Agfa 400, rated well below 400. Agfa 400 seems to age badly in comparison to HP5 and Tri-X, or maybe it was just the stuff I tried.
2475 recording film hasn't been around for some time, unfortunately. It was only available in 35 mm to my knowledge. 2479 recording film is still listed by Kodak, but only through a government contract and not in 120. The 120 equivalent of 2475 was Royal-X, a 1250 box-speed film. I threw out all but one of my last rolls of that in a move in '97 - it was a favourite of mine for use at night in an Autorange 820 before Delta 3200 became available. If you can find some usable Royal-X you've got grain.
'The down side was that it also tended to produce white lips, which had to be avoided by using grey lipstick.' Good news! I've heard that M·A·C have both 12½% and 18% gray lipstick in their spring 2005 collection, after sucessful lobbying by liberal APUG members.