Which official Dragon Ball crossovers are there?
As per the one piece fandom wikia there is only a single dragon ball crossover with toriko and two more episode with the toriko in anime.

There is a collaborative work from both the writers of respective manga called cross epoch featuring dragon ball and one piece.

References:

https://onepiece.fandom.com/wiki/Cross_Epoch

https://onepiece.fandom.com/wiki/Category:Crossovers