My experience suggests that there are usually some essential central cultural standards, stories, and themes that need to be understood and absorbed across all of the businesses. At the same time, some of the cultural strengths of the acquisitions could be energizing and provide needed new perspectives to your manufacturing genes. For instance, my friend, Bob Chapman, CEO of Barry Wehmiller Companies, is an advocate of lean+people-centric leadership. The hybrid is enormously successful for them (with more than 60 acquisitions) and informs their 100 year old manufacturing culture to great organizational and financial benefit.
A terrible percentage of mergers and acquisitions fail specifically because they couldn't merge their cultures successfully. In all of the M&A culture work I've done, the parent firm says all the right things about learning from their acquistions, but nearly always moves immediately to erase anything that doesn't fit the old mold. It's truly rare that they actually sit down and perform a joint strengths analysis that engages both groups and develops a new concensus about their combined strengths, their aims and crafts interactive agreements for how they will go forward.
Without that kind of explicit, open analysis, visioning, and ground rules, you generally end up with covert resistance, toxic politics, and even sabotage of corporate initiatives. You lose great people who are looking for healthier working environments and transparent functioning, and the much-touted advantages of the merger fall far short of the hype AND the potential.
So, I suggest that you engage in the kind of joint examination of cultures and visions that can net you the best general concensus on what everyone really needs and will thrive under. In this process, you can focus on the most powerful positive gifts of the players, harnessed for a common goal, including, as needed, different flavors of the new combined culture in your different businesses.