Probably not a 235. Chevy introduced the third generation 6 cyl in 1962. It came in 4 displacement sizes: 194, 230, 250 and a tall deck 292 cu in used in 5000 and 6000 series trucks. All these engines (except 292) used a shorter stroke and had 7 main bearings (up from 4), and steam vent ports between the cylinders for much improved heat dissipation. A quick glance at the much narrower valve cover than gen 1&2 sixes will clue you in. The narrow valve cover was possible because the rocker shaft valve system was upgraded to the ball socket style like the V8's.
With the right trans and rear axle combination I'd feel comfortable on the road.
Parts are cheap and still readily available. Most of these engines had a 2 piece cyl head intake manifold set up plus an exhaust manifold--all still available.
On the other hand there were a few motors that had the cyl head and at least the intake manifold cast as a single unit. These heads are difficult to come up with. I can't say with certainty that the one piece heads weren't used on the buses but I really doubt they were.
Jack