B21/23 block will use a 1/8npt 45° angle adapter. Same thread pitch on each end. You could just screw the sender into the block, if it could fit in the space provided.

It's just as well that you broke the fitting. They aren't very strong, and I would have suggested replacement anyway. The vibration fatigues the brass. When I've removed these senders from cars in the junkyard, I just use a breaker bar or piece of exhaust pipe to push against the sender to break the brass adapter. Works every time and it's MUCH easier than trying to unscrew the sender.
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forums.turbobricks.com

When I went to look for them, it turned out to be easier than I had expected, as a local auto parts store had an assortment as a reasonble price.

Another possibility is an place where air conditioning mechanics get their parts. they have quite a variety of adapters and nipples.
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jds

I have an extra set of just such a set up. I think the elbow has reagular automotive type threads. Take the broken pieces plus the sender to your favorite auto supply store and they should be able to get you a match right away. At least we did, when I worked as an automotve counterman years ago.
buena suerte,
el raidman