I'll ream the ends of the tubing, and turn the pushrod shank to get about a .0015" press fit or so for about 1/2" on each end. Then it's just a matter of fabricating a holding fixture to stabilize the end of the tube while an arbor press does its thing. Virtually any fit problem can be solved with the judicious application of high speed steel. Other difficulties respond better to high speed copper and lead.

"There's very few problems that can't be fixed with a 1911 and a .30-06!"
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!