Early Slant Six A/C Success
1. Not sure what you mean by "engine to firewall" issue. It's an "engine to radiator" issue. The 1961 Lancer and Valiant were early, Chrysler "compact" cars, and it's my understanding that creating room inside for 6 people meant shrinking the dash, putting the heater on the firewall, and, in general, shrinking the amount of room in the engine compartment to minimize the overall length.
The Nostalgic Air compressor mount system is designed for later Slant Six models where there was more room between the engine and the front grill/radiator/radiator cross support.
2. The crank pulley must've been from an A/C car originally. I can't say for certain whether or not the engine is original to the car. I only know it was rebuilt in the 1980's.
The issue all along for the 1961-1962 models is a cramped engine compartment.