I have seem both types on GM cars of the era. Ames list the blade style
https://www.amesperf.com/parts/53918/ as "1967-69 CORRECT TEMP SENDING UNIT-ALL WITH RALLY OR AUXILIARY GAUGES". The button style
https://www.amesperf.com/parts/63582/ is listed as "1965-72 TEMPERATURE SENDING UNIT WITH RALLY GAUGES"