To be honest I dont think you should clock a 68k+ppc that high unless you really know what you're doing and dont mind if it burns. Delshay has several cards and is apaprently a very skilled overclocker. You could consider the 'stachu' mod if he still does them, since this only affects ppc and is supposedly very 'safe'. I dont think delshay ever clocked a card for someone else?
As for people having told you not to invest in a ppc card for your a1200, think again. It is the best way to upgrade, it will give you 060 and RTG graphics, access to OS4.1 (it really is fast enough now!) and you can still turn it off with a keypress in case you need to go back to that 020 cpu. I would never get an a4000+ppc setup for just that reason alone! And I say this after having burned 3 bvision cards and taking more than a year to get this whole OS3.1/3.9/4.1 system running in perfect harmony. It may be hard to understand, but it was FUN!