temperature sending unit

[Kent66610]

Swapped 250 for modern 350 fuel injected crate engine in my '67. Temp sending unit too large to fit location in block, so temporarily located it in water pump, where temp is always low because it comes directly from radiator.
From other sites, it seems that sending units and gauges must match ohms, but I can't find anywhere that tells me resistance of stock gauge.
Can anyone give me a manufacturer and part number of a sending unit that fits and will match my gauge?
Kent66610