Just a note on the non heat passage intake manifolds. You can really tell the development on these wasn't done in the northern states. Here in Michigan blocked or non existant heat crossovers don't make it. From mid November till mid April. Any time the air gets below 35 degrees and the humidity gets high you have a softball dize chunk of ice for a carburetor in about 20 miles! At best the throttle plates freeze and you can't slow down the motor or the idle circuits just freeze up solid so you have to let it set 15-20 minutes to melt. Then refire the water-gas mixture in the manifold. The only way you can drive these is with an Afro-engineered hot air intake off the top of the headers or exh manifold. Duct tape and dryer vent hose works well! Been there many times thru many rods, in my misspent youth!!