Just get some new hubs, many different hubs fit your axle.
83-85 200x
86-87 200x about 1-3/4 longer than 83-85 200x
300ex
400ex
86/87 trx200sx about the same width as 83-85 200x
250x
A few others too......
I run aftermarket trx200sx alum hubs on this 83/84 250r axle, from outside of hub to out of other its 33-1/2 long.
If I put 86/87 200x hubs on it would be about 35-1/2 long out to outside of hub
I don’t think it’d be worth messing with replacing studs (just get new) you won’t be throwing tools around the shop this way
Shep