Slant Six 170 vs. 225

When I got the 70 Duster it had many miles on it, 300 thousand or more. 3speed on column, was so wore out at the bottom I had to shift real easy letting it drop in next gear or pull over and get it out of two gears (carried a long screwdriver for that). Took the stock carb (Carter) replaced with the Holly, ran twice as good. The lady bought it new ($2700). AC and turbo looks like it might be hard to do?!