Following are pages from each of the original 430, 530 and 630 parts manuals. These are the manuals printed for the launch of the 30 series tractors. Later, after the 630 was discontinued, Case printed combined parts manuals for the 430 & 530. The first of these was Catalog No 963 which superseded the original manuals and covered up to serial number 8262800 (1960-1964). The second is catalog No 944 which covers serial numbers 8262800 through 8297800 (1965-1966). The final catalog is No 979 which covered serial numbers 8297801 and after (1967-1969).
Note that in all the early parts manuals, a flywheel for the diesel engine with a 10" clutch (part number G11864) was common across all three tractor models. Similarly the diesel tractors with an 11" clutch all showed a flywheel part number G11859.
Two other items of note:
1) All had the same 135 tooth ring gear. (p.n. G11710)
2) The flywheel for the 10 inch clutch was discontinued before (or when) the newer version parts manual was released. See last page below...(which is the same as the early parts manual at the Case website)
If I were a betting man, I would wager Case decided to no longer carry two different flywheels and adopted the 11 inch version for all tractors regardless of clutch dimension. Further, I would speculate that either flywheel would work on your 630 since it is a 10 inch clutch. Lastly, other than the timing marks, I would wager the spark ignition and diesel flywheels are exactly the same design.... I've had a flywheel from my 630 and a flywheel from a 351 sitting next to each other a few months back and I could not tell them apart except for the timing marks (my 630 is a diesel, and the 351 is a spark ignition)