Jamie '87 CGT

OK, i have a 87 coupe gt, manufacture date is 9/86, i went to order a cv axle and they need to know my chassis number, i found it, and its nothing close to my optins, option1 is #81d077974 or option2 is #81d77973, i went ahead and ordered the one ending in 3 assuming it is for an earlier chassis and my car would be earlier since its not a 87.5, any info would be cool to know, JP