[Cliff R]

"What is the best way to tack the pickup tube so it doesn't fall out or shift out of place?"

I would NOT weld the pick-up to the pump for any reason. I see this recommended a lot, but I've had enough engines come in here where the weld broke off a piece of the pump and the pick-up ended up in the pan to avoid that deal altogether. While on the subject NEVER weld the retaining ring on a TH400 drum for the intermediate sprag either, get the 4L80E spiral lock. Seen WAY too many of those have the sprag knock the welds off the ring and the trans looses second gear and has to come out for repairs.

Several much better methods to accomplish that task. For deep sump pans with the taller aftermarket pick-ups I weld a strap to the pick-up then put the other end under one of the pump cover bolts.

For stock pick-ups they are driven in place, then I drill a small hole thru the pump and pick-up about 1/4" from the edge and tap it for a hardened allen drive machine screw, usually 8-32. This is done in the shop vise, then the cover removed to blow out any chips that may have fallen inside.

With either method the pick-up can't fall out or turn and you aren't putting any heat on the pump from any type of welding operation........Cliff

Attaching the pick-up didn't happen from the factory, but the material those OEM pick-ups were made from was better. Aftermarket pick-ups are "soft" metal and don't have any "memory" to keep them in place, so it is imperative that you take the extra time to make sure is doesn't fall off and end up in the assembly.......Cliff