my duster is 100% stock, slant 6 1bbl, stock iron case A833OD, 3.23 rear.
back in the early 2000's, I built up a 5th avenue with 3.55's, a 42RH with an 1800 RPM lockup converter, and 3.55's. the first engine was a stock bottom end, reringed 360 with headers, and edelbrock air gap, 600 AFB and a comp XE262. replaced that with the original 318 bottom end, lightly ported magnum heads, same intake, carb, headers, but a custom grind on the stock roller cam that was 208/212 @.050, but with more duration @.200 lift than the XE262 and like .050" more total lift on the stock cam's factory 112 LSA, installed at 106. butt dyno, the 318 pulled at least as hard as the 360, but had much better manners, especially off idle, under 2K RPM cruise, and gained like 4 or 5 MPG....