Help needed; gearbox drain plug. Rb30 manual box.

Ok, Chaps. Tried to undo the drain plug, and it started to strip the 1/2 inch hole. Took it to the Mech, and he couldn't budge it. He reckons to grind a short bolt to fit, and weld it onto the plug. Went to a fabricator/ welder, and met a fleet maintenance bloke there. He reckons a 6 inch flat bar with a hole big enough to weld around the lip of the plug is the go. Any thoughts on a better fix?
Also , is the fill plug the same size as the drain plug? Cause I can take it out and use it as a sample to get a replacement one for the drain.

Mine was seized on my zd30 box I welded my old half inch bar in it and tured it with a breaker bar putting the heat in also makes it easy they should be the same sizer with the drain plug being magnetic

Use a hammer and drift to shock-load the plug. Make a larger tool that fits a snugly & use a hammer to firmly tap while putting a torque on it.
Hearing might work, as it will expand the ally quicker than the steel plug.
Loctite sell a 'freeze-off product that works a treat & will probably shrink the plug. I would be surprised if this doesn't work. Last resort I'd weld a socket or decent sized bolt to it. Keep a extinguisher free.
Once the plug is out, repair or replace it & use loctite 567 thread sealant.

I tried drifting and shock loading but had to weld it. Problem is people rattle gun them up or over tighten they are a tapered thread nip it up then crank it half a turn more that's all it needs any more you'll be having the same problem

Thanks, I watched the mech shock load it. He put a lot of energy into it, and eventually his boss stopped him, because the breaker bar was flexing badly. I will have a look into getting the Freeze off.

Don't shock load it with freeze stuff you might crack the casting. Welding it is cheaper

Yippee, Cost $45 ( the workshop minimum is $80) but the welder also used one of his sockets to weld on the plug. After it cooled, he used a dirty great breaker bar to get the plug moving. So thanks to Portland Fleet Maintenance for helping me out. All I have to do now is source a new plug and the correct grade oil, which I'm dealing with on my other post.