Looking for part number choke thermostat for 63 170

The Holley and Carter choke thermostats are fully interchangeable without problem. The bigger variable is exhaust manifold style. The choke mounting pocket groups are '60-'65, '66-'69, '70-'72, and '73+. All Slant-6 exhaust manifolds fit all Slant-6 engines, and many early manifolds have been replaced with later ones, and the only type of exhaust manifold generally available at this late date is the '73+ style. A '60-'65 choke can be tweaked (one mount hole ovalised) to fit a '66-'69 exhaust manifold, or vice versa, but it's no-go for a '60-'69 choke thermostat on a '70-'72 or '73+ exhaust manifold or vice versa.

The easy route: get one of the Electric choke kits. Use № 1231 no matter what type of exhaust manifold you have. Easy to install, and unlike the factory type unit it can be adjusted easily from up top without having to remove it from the exhaust manifold.