This is a totally different question than what the OP is asking but you’re supposed to have ~1”. But that has nothing to do with the seal. You bottom the yoke out in the transmission, then slide it back 1” and measure for the driveshaft with the yoke in that position.
I don’t know what kind of seal you have, I’m not gonna assume they’re all the same. But if the yoke is compressing the seal when the driveshaft is installed the driveshaft is more than likely too long. My experience has been that if the rear seal is installed it has to be compressed significantly to bottom the yoke, but with the correct length driveshaft installed the yoke is not compressing the seal at all, there’s a gap before that happens. Again, I would not assume all the rear seals are the same.