the 250's problem is the intake manifold too far out to the side, at least with my 67 ... I scrounged up a shroud piece that was a sheet metal plate that cupped the exhaust with a tube out let on one end that fed up into an inlet on the underside of the air cleaner snout, which had a thermostatic flapper so that when cold it draws air from the warmer manifold feed, then when it heats up enough that opens to allow air intake in the usual way .... if that's clear - I forget what year the setup came from but I think some later truck .... I swapped a 327 in finally because I didn't find the 250 strong enough for what I did with a 3/4T [heavy loads uphill], even then I didn't like the truck
just make sure it's well warmed up before you head out, don't expect to just fire it up and drive like with modern computer controlled vehicles
Bill
