If you get an after market pick up tube that is only held on with clips, I'd do what Blue recommends and tack weld it. I wouldn't trust something as important as the oil pick up tube to clips.
I could just see bouncing your tach off the rex. limiter trying to get through deep snow or out of a deep mud hole and them clips letting go and starving your fire breath 4.0 for oil. that would be UG-LY!!!!