What's the easiest way? Just set the cup with bearing end down on the workbench and slightly flare out the bottom of the cup with the right size socket or flaring tool. Or as bubba G would do, just bend it out a wee bit with two sets of pliers/vice grips.
I'd prob do the same as this, flare em out a bit. but first i'd be carefully tapping the head tube in, with a light weight flat side and round side ball peen hammer. gentle taps and patience. . use some leather and or soft pine on the painted tube so ya won't knock or crack the paint. and as the head tube is thicker, harder to reshape, knock the top side cylinder of cups into a slight oval then oval out the middle to get em balanced 4 sides and or 8.. Paints and glue might be the easy way out but much weaker than metal against metal. Murphy likes that. (murphy's law) glue, epoxy and paints as fillers on metals especially old just don't stick. hot lead is better than that plus, you can sand or grind it back down wit wood pole to hoone it into right size. or just roughing it wit dremmel type tool to get the right shape.but kisa your paint good bye. 'bah, bah, bye,' bye!'. Aluminum cans for shimming not good, aluminum and steel causes electrolysis,, eats both> refer to murphy.
Of course your best bet is to buy a perfect shaped mold and squeeze em back, but that's if ya want to buy a tool you'll have to look at for the rest you life. but if ya finds some realy old, hardened wood, and a friggen drill bit that;s tough enough to drill all the way through it, then cut in half, wala!
Wood Species Specific Gravity* Compressive Strength (psi)
Hickory -------------0.72 ------------------------9,210
Maple, ---------Hard 0.63 ----------------------7,830
Maple,----------- Soft 0.54--------------------- 6,540
Oak, Red--------- 0.63------------------------- 6,760
Alternitively Practice with a ball pin hammer on sheet metal, you be surprised how many things you can reshape wit em. I don't seem to have the patence or skill I did as a teen through my late 50's but dam I used to tap some sweet smooth into chrome fenders and stuff like that. Painted is much easier as not so much shine to see the tapping, and if done right, soft and gental it'll retain it's sticking to the metal and you can buff out your marks. but chrome,, you had to get up real close to see my signature. But still I'd guess I could knock around t he head post some and flare the cups to fill the gaps and stick those puppies. Keep in mind that, when you bend steel back without hard steel behind it, which continues to temper/forged ( squish them crystals tighter) , , you've taken it's temper out,, it would require re-tempering or forging (squish crystalline tighter ) to harden it back, so, Murphy's in play. So try and keep steel behind the metal you're screwing up.
I can remember NOT having a ball peen in my tool box, or my dad's since was a wee child, no craftsman/or wo, should be without em