Question about two SCBA tanks

I have two tanks from new old stock San Cheong SCBA kits. One (black and white) seems like it has a normal neck and port size similar to my Joe Brancato Guppy tank. I assume I can just remove the existing valve and slap a new fill station and be good to go. Is that correct and are these normal righty-tighty, lefty-loosey threads?

The other tank (gray) has a larger neck and the port size looks different. I am pretty sure this has a CGA-347 fitting, but the threads seem damaged because it doesn't allow known good fittings to be attached to it. I'm not sure how to fix this, maybe a thread chaser, maybe taking it to a firehouse or gas supply company, no clue. It may be hard to tell from the photo, but are these both standard (M18*1.5 ??) port sizes with just a larger neck on the grey one? Any recommendations of fixing the thread? It behaves like there's not a starter/cut thread there.

Thanks!

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I'd send that pic to Joe B. to get his opinion of what you have going on there. I haven't seen either one of those valves before. The one on the right does resemble a CGA347 style. But, the left one looks more like a DIN fitting to me. I also haven't seen an SCBA with the valve on the bottom like that before. I've seen valves there on SCUBA but, not SCBA. 

Can you contact San Cheong or visit a website for info? 
 
Left tank is DIN 300

Right tank looks like SCBA

If your trying a Chinese SCBA attachment be advised I have had some issues with Chinese CGA347 fittings not made correctly and this gave the appearance of damaged threads. (this was with E-Bay sourced Hand Tight fittings)

Likely if the cylinders are not of Chinese origin then the valve thread into the bottle is not M18X1.5. The fireman tanks in the USA are usually 7/8" and Paintball tanks are 5/8".
 
Rather than changing the valve on the bottle on the left, you might find it cheaper to get a DIN fill adaptor. There are plenty available with or without hoses. You will probably find that dive shops prefer that type of valve. Just make sure it's Din 300, not 200, it will be stamped. Here in Australia, our SCBA tanks are all DIN valved so we don't have the compatibility issues that you guys deal with. We do however have the issues with metric and imperial neck threads on different brands. 
 
The one on Right looks to be a 346 fitting not a 347. 347 female WILL work on a 346 but NOT vice versa. Left one looks like a DIN but not being experienced with DIN fittings I wouldn't swear to it.. I have a 346 female I'd be happy to give if you want to try it & see if works "mo better". Let me know, shipping should be nominal.
 
Good catch Gerry52, the threads do look shorter than the 4500# CGA 347’s. If you’ll notice too the gauge and label indicates a lower pressure bottle. The 300bar label shows that it’s good for 4350# working pressure but the gauge is showing that the intended use required lower pressure, maybe 2600# as some of the lower pressure SCBA’s are designed around. 

Jking