I have a stock FJ40 setup on my 74 using the pressure/return lines from the carb and a stock mechanical fuel pump. I've never had a vapor lock issue either and we wheeled at or above 11K to 12K feet on the 40's only run when a number of other rigs did have issues.
I do have an HEI distributor, I ditched the stock exhaust manifold and installed a header, and I have a liquid heat riser installed on the bottom of my intake manifold.
I believe the liquid heat riser makes the biggest difference. Yes, it helps the rig run better in the winter by warming the base of the intake manifold, but it also keeps the manifold base cooler by ensuring it never gets any warmer than the engine water temp of around 180 degrees.
I guess it's possible that running that different fuel setup helps by increasing the fuel pressure inside the carb to help prevent the fuel vaporizing as easily.
Randy Rosetta KDØKWX TLCA #19351 NOW 2015 Rubicon Hard Rock & (2) 1970 Boss 302 Mustang's THEN 69 FJ40 Buggy "Meanie", Mini-truck "Gecko" & 74 FJ40 "Blue Mule"