To reply to Lee's statement I an earlier post. There were 2 different sizes of FIM coolant tanks. The thinner one being more prevalent (it should be black BTW). They are getting hard to find as they are also found on Bizzarrini and Ferrari cars of the period. Pic of a NOS tank I sold a few years back.
As to the side gussets, these are a modification on later cars, maybe to correct what early road tests claim cars could over and under-steer at the same time.