Muti-Plant Management

Our corporation is acquiring another company that has two
manufacturing plants. My intentions are to set them up in Vantage
(V4.00.904) as one company with two plants. However, I am having
problems with the logic of the G/L account structure as it pertains
to product groups and class. Is it best to set up separate product
groups and classes specific to each plant with the G/L structure to
match? What if parts are switched between plants because of available
capacity? Any input on would be greatly appreciated.