AFAIK Krieger still makes the accumark barrels.
But
If you are interested in the 28-Nosler, the only choice after the 7Weatherby (LOL/not really), Benchmark, 8, 8.5 or 9 twist.
They can do a Weatherby #2 profile or an Accumark/#3 profile.
Changing to 28-nosler requires 3 simple things you or your smith can do.
Remove the spacer in the magazine box.
Replace the follower with one for a 300 Weatherby
Extend the bolt stop slot in the bolt.
If you go with a #3 profile barrel, some inletting work will be required.
Take this as you will, I have more than 5 Mark Vs. I have made 4 versions of the xx-nosler including the 28 (7mm). If you open your project up to a different cartridge, IIWM I would go:
28-Nosler
26" or 28" (28 preferred by me)
Benchmark barrel
8 twist
#3/Accumark profile or Sendero, fluted.
Float the barrel
Check the bedding - would probably bed the full action
This better be what I would do because I'm doing it. Except this time the barrel will be a Proof Research.