HELP!!! Flintstones Floor Pans need help fitting

[Rl350ss]

I was about to start and LS swap on my 88 MCSS I pulled out the carpet to find I have a limited edition Flintstones floor pan so I found some pans from a donor car the only problem is the guy who cut them out for me didn't leave much room on the sides to work with I cut out the old floor pan making sure to leave some extra metal on to work with but ok having. A lot of problems fitting in the donor pans I don't know how to work with the sides should I cut them off or cut into the old cars rockers panels I took pictures so you guys can see what I'm talking about I traced around the donor pan and laid it on the rocker panel so you guys can see. Any advice or tips will be welcome I just wanna fit this in so I can weld it down doesn't have to be perfect just me up hold me up while I drive
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