yes it is required to match each detail of parts otherwise there would be some serious problems. I have faced this situation earlierYou would need a parts book, Buick of course, & look up all the parts needed & compare parts numbers. I know that the A/C compressor will be the same. Not sure of all the other parts involved. Would be BEST to find a '65 Riv. that has all the car parts you need so your not chasing your tail on parts. On that note I have a '65 Riv. GS that has all the parts needed. I live in Ct. so depending on where you live shipping costs could be the deciding factor.
Tom T.