Ooooh..... first time I have seen a BL630.

I have heard of a BL234 (but never seen one), but not a 630.
The BL pumps are Hilborn, and predate the PG series pump. I have a BL420 here that I rebuilt and had flow tested. Through the HAMB I know of one being run on a Dragmaster FED, and another just unearthed on a set of flathead injection. They are funky internally - sliding vanes, and a carbon volute.
At one stage I needed to reverse the rotation of the pump. Called Hilborn (from Sydney

) mebbe 10 years ago. They left me on hold for about 30 minutes. Started to get worried, as I could hear Telecom (the Aussie cousin of Ma Bell) in the background laughing and counting out my call cost. They came back on the phone, and told me they could only find one person in their workshop who had ever worked on one. The answer to rotating the pump is to press out the carbon volute, turn it 180 degrees and press it back in. The chances of cracking the carbon are high, and they are no longer available. Needless to say, my pump still rotates the same way. I was really impressed that Hilborn went out of their way to find me the answer. They were good people.
I've got some flow test results, and a detailed step-by-step overhaul document I wrote (lots of pictures, and some measurements for example on the drive tang). They are in pdf format, and I can't work out how to post them here for you. If you want a copy, PM me an email address and I'll send them through.
Cheers,
Harv