You can plumb a T or Y into the front or top of the intake and run 2 sensors.
If the car has a 2 wire factory sender that goes to the ecm you can't splice into those wires and expect it to work right.
3/8" NPT threads are in the block, you might have to bleed the two senders you install outside of the water flow but they will read within 5 degrees of the block once the water goes into the external plumbing.
You have to measure everything carefully so you have room to spin the senders on and install the brass fitting.
Here's the name you can search for for the street T brass fitting, the one listed is expensive but well made.
Home depot may have something cheaper.
Anderson Metals-06127-06 Brass Pipe Fitting, Barstock Street Tee, 3/8" Female Pipe x 3/8" Male Pipe x 3/8" Female Pipe
This of course assumes the aftermarket senders are 3/8" NPT which they most likely are if they fit the block hole.