Press fit suction tube- GM type 2 pumps
It turns out the suction tube is a press fit in the bottom of the pump suction opening.
Good news- A suction tube is available from your Chevy dealer- its for a "late model Corvette", part # 26006074. I called the local Chevy dealer, and it's available. Bad news- it lists for $42. That's more than I paid for the pump! they wanted $34. Too rich for my blood. I used a brass 3/8" npt X 5/8" hose barb ($3.05 at Lowes). Half inch hard copper tubing fits into the back of the hose barb- I soldered it in- and the 3/4" projection I left pressed into the pump suction opening very firmly. I had to grind the 3/8npt threads down to fit into the top part of the pump opening. I used PC7 to lock the brass fitting into the pump. ( I'm not planning on taking it apart)
There you have it. Good to go. Total cost $3.22, with tax.