need to know if these two vehicles tires and rims are interchangeable, l have brand new tires on the merc and would like to put the custom rims on my ford truck.Both vehicles use same size tires, l know l could put the tires on the truck rims

no

No, u could swap the tires only if they r the same size. And u would need to make sure they had the same load rating & speed rating for what the truck calls for.
But the rims would have a different bolt pattern & a different style of lug nuts..
So l would swap the tires if they r the same size & type, unless ur customer rims r the kind that have different bolt spacings, then it might work, but l would contact the manufacturer of the custom wheels & just ask them before u swap them..Losing a wheel at 60 is not very fun!