help please,4 speed conversion qusetions

the only change in the 340 crank shaft was in 1973,,prior to 73 all 340 were steel forged cranks,,,in 73 some,, not all are cast cranks,,if it is a cast crank,,it will require a externaly balanced fly wheeel,,such as a early 360 non magmun style

if it is a 68 thru late 72 340 steel forged crank it will use the non balanced fly wheel same as a 318 340

cast crank engines, use a crank shaft dampener with a weight,,
also make sure you get the correct fork,,,

floor humps are available from brewers i believe