If you search on this site I wrote a post where I used math to show just how much weight affects motorcycles. What I showed was that for a cruiser, about a 250 pound rider is where a 250cc cruiser starts being slow enough that I wouldn’t be happy on it in traffic. So, for a 300 pound rider, I would go up that next step to a 500/600/650.
My suggestion would be a Vulcan 500 (wide tank, feels like a much bigger bike), or a Shadow VLX (600) is he wants something slightly more narrow.
The S40 / Savage 650 is a pretty small bike, it is closer in feel to a 250 than the rest of the 600ish cruisers. So going with one of the bigger ones may be more comfortable. But I’m 6’0″ and can sit on an S40 without issue. A few people on this forum started on the S40s and loved them. The lower weight seems to make it a good starter bike even if it is a 650cc engine.
I have no experience with the V-star, so I won’t offer anything there.
The big thing is, try on as many bikes as possible to find what is comfy, and keep the CCs to a minimum. A salesman will tell him he’ll want a 750cc or 900cc bike because of his weight, and I think that is bollox. And of the 500/600/650s wil have enough power to move him around faster than traffic (andif he’s looking for more than that, he’s looking at the wrong style of bike to begin with).
Elwood wrote a really good bit on starting out on a sportster 883, and I suggest you have your friend read it:
“The two seconds between ‘Oh S**!’ and the crash isn’t a lot of practice time.”