welding gurus Tig welding to then cut thread

Ok guys,

Have a bolt that I cannot replace, its to hold on the oil filter adaptor, long story.

To cut it short I needs to change a thread from 3/4" to super obscure 13/16" which is a tiny bit bigger (about 1.6mm).

The "Bolt" is hollow" as in a banjo bolt.

I could cut the 3/4 threaded section off and then tig the 13/16 section on.

However I do have a 13/16 die and feel it would be stronger to not cut the threaded section off.

Instead tig over the threaded section, then surface grind to 13/16" then cut a 13/16" thread on the tig'd section.

ANy tips or advice would be good, thinking of heating up before strarting the tig, or on the lathe taking off the original thread before laying on the thickness to retap.

Advice people

here is the bolt with the thread section