ballpeen hammer will work

I have use a large socket against the tube also to get a rounded dimple large enuff so I did not have to beat the tube with the ballpeen so much

I would remove it(I know you dont want to) place 2x4 behind the tube

I would hate to heat and beat for clearance and gain an exahst leak at the engine flange..DAMHIK

wound up pulling it,rewelding all the way around the #1 tube and engine flange cause it dimpled at the flange close to were I need the clearance

good luck with it