seal kit questions for '66 20 hp.

HI all. I was reviewing the replacement Siearra kit #18-2684 for my '66 20 hp, per the iboats store's suggestion, but it seems like the part numbers are different from those in my exploded diagram/manual. For example, the drive shaft seal is listed as 307563 in my manual, but that part number, or its Sierra equivalent, does not appear in the iboats kit? :/ I also noticed that my motor's drive shaft bearing doesn't seem to have/use a prop shaft oil seal, which seems odd. Could this be right? Perhaps the bearing was replaced over the years with on that doesn't use a prop shaft seal? One more thing, do the Rev gear and rev gear bushing need to be two separate pieces? They appear to be separate in the exploded diagram, but they are stuck together in my gear set. The gear spins pretty freely on the prop shaft despite being stuck to the bearing, but it is a tiny bit stiff. I'd like to try to separate them, but I'm not exactly sure how and I'm afraid I'll damage the bearing and/or the gear trying to do so. I'm tempted to just leave it be, if y'all think that would be ok? Sorry, one more ting. Does any one know the exact dimensions for the screws that hold the plate on the shift rod coupler window? I have the part number, but not the dimensions. I'm thinking (1/4 x 20 x 1/8"), but that's just a guess. Whew! Sorry to ramble on, but I 'm just trying to get my LU squared away. Thanks for any help!