VA360 was a side exhaust port engine while the VB is centre port.
Completely different frame, swingarm, suspension, forks, triples, seat, air box and as you said pipe. Basically some of the engine internals carried over.
The bike pictured also appears to have the incorrect front end as the fork tubes on the VA360 extended about 75mm past the top triple clamp so the bars where offset to the rear of the triple clamp and the fork legs where a different type from memory. The pictured bike also has a VB250/360 fuel tank while the VA360 had the same tank as the VA250 only with black / yellow stripe as pictured.
The pictured bike also does not have the engine speed clutch that all OZ VA360 came with although some were retro-fitted with the arrangement on that bike. There is more interchangeability with the VA250 as far as chasssis goes than the VB360. The VA360 cylinder and head are one off I believe.
The VA360 was not the best Montesa ever built but were fast in the right hands but outclasses in 1976 by the RM370A among others. They are a pretty bike though like a lot of the Spanish bikes.