The new manifold is a '73-up type, which requires a '73-up type choke thermostat. The factory items require correct hookup of the electric-assist heater or the choke will be too slow to open, wasting gasoline and diluting your engine oil. "Correct hookup" means you need the choke heater modulator dingus between your source of ignition-on +12v and your choke thermostat.
The '73-up cars have a bad reputation for cold-bloodedness (bitchy cold start/poor cold driveability), largely on account of these troublesome, nonadjustable chokes. Save yourself a great deal of aggravation and put on an
adjustable electric choke kit. You'll need a kit № 1231 if you're running any up-to-'73 1bbl carb (Carter BBS, Holley 1920, Stromberg W) or a 1974-up Carter BBS. You'll need a № 1234 if you're running any other '74-up 1bbl (Holley 1945 or 6145). You'll need a № 1232 if you're running a 2bbl (Carter BBD, Holley 2280). Any of those three E-chokes will bolt onto the '73-up exhaust manifold you're running.