Damn, the more I read here about 5-speeds, the more confused I get. I have what I believe is a 63A 5-speed box. As luck would have it, I purchased a Morris Minor Van from a fellow here in the US, and he begged me to take a Datsun motor and box he had purchased that he planned to put in it. I almost didn't pick them up, but I am glad I did.
Another thing is I believe this box has a sand-cast housing. Compared to the other 5-spd I have, (stripped from a '79 210) there is a big difference in the look and
feel of the housings. This one is very textured, and the other is very smooth
Here's the box in question:

Here is a link to what is identified here as a 63A and I believe they are identical. (Mine obviously hasn't been cleaned)
63A pic on this siteI apologize in advance for riding this little pony too far, but do I have a 63A here?
Thanks for your help!