Sometime around 1970 I bought the first 340 6pack motor that hit the salvage market ($700)over the next couple months went through a few 7 1/4s. Then picked up an 8 3/4 out of a 59 Savoy? To wide,and rubbed the fuel tank but made it work with a tank from a 62 valiant.Then during the blower build,I picked up a 44 from an IH scout 2 and narrowed it myself and resplind the axles.I figured that a 44 in a valiant was = to a 60 in a road runner.So far all is good, all though it does have a twist in an axle now,so a set of Moser's are in the works.