Howdy LaGasta;
The #1940 will have a SCV and linkage that will match yours, assuming it was ordered as a replacement for your '63 170. If it was not specifically ordered for your engine, there is a likelyhood that it will still work. The 1940 model is a FoMoCo replacement for '60 to '67 Autolite 1100.
The #1946 was the last carb used on the small sixes before it was discontinued. It began to appear as a replacement for the Carter YF in the late '70 and remained uptil 1983. It is a much more complex and sophisticated carb, but was encumbered with thermo, vacuum and electronic feedback systems as a response to EPA regs. Later got worse.
when all is working as designed it is a fairly successful carb. It, like all the rest is weak in the accelerator pump area and susceptible to dirt and wear. Later models are less tuneable.
The #1946 is designed for cable linkage and uses a unique carb to manifold adapter. It has a very nice and efficient hot/cold air cleaner system. It has no SCV, but is tapped for ported vacuum to the distributor.
Adios, David