Both the Rochester 4-GC 7005100 and the Carter WCFB - 2005S were used in 1953. Neither was designated to be used exclusively on Eldorados. There were no engine options in 53 for any model. All used the 210 HP, 331CI engine. Both the Rochester and Carter carbs had slight design changes to match the operating characteristics of the higher compression engine used in 53. So says the Shop Manual in the 53 Supplement section. I believe that on any given day, whatever carburetor was available that day of the build, was put on. It does seem that the Rochester was used more often though.