I've done about a half dozen mix-n-match Shimano freehub swaps with non-spec'd freehub bodies in the last year or so.

There are a few differences when going from an old 7 speed UG/HG freehub body to an non spec'd (Shimano Tech Docs compatible) freehub body whether another 7 speed or an 8-10 speed. The first hurdle is getting the right flange to match your current freehub. Shimano made shallow and deep flanges. Yours looks to be a shallow flange.

The next, and somewhat irritating change, was a different diameter dust seal on newer, (late 90's+ ??), freehub bodies. This basically eliminates using your original.

And get a Hyperglide-C freehub body, mid/late 90's to present, so you can run an 11t.

The best, or at least the easiest, is to "FIND A COMPLETE FREEHUB" and move the freehub body, DS cone, seals, spacers, and axle over to your old hub. You might be able to use your NDS spacers/wahers, (you will need to use your NDS cone and seal), or move whatever is needed over or do anything that gets you to 130mm OLD. You will have to re-dish your wheel by a couple of mm's.

I needed to go the other way and swapped out a freehub body off a 10 speed FH-5700, and mounted a 7 speed freehub body off a FH-1055. The FH-5700 would probably be a good choice, BUT you have to decide what will work. Once again get a complete freehub.

The one of the right is a UG/HG 7 speed deep flange, center is a shallow FH-1055, right is a shallow FH-5700.



John

Edit Added: As I re-read the OP’s original post I missed that it was a mtb. If the OLD is 135mm, you can use the current axle. It doesn’t matter if you use a road or mtb freehub body as a number of the early ones were spec’d on both.