64 F100 master cylinder conversion

[64steve]

Hi everyone!
I have a 64 F100 and my master cylinder is slowly going bad , i wanted to upgrade to a dual bowl style but having slight issues , issue number one is i bought a 67 289 mustang master cylinder part number #MC36222 and fits but the rod is too long (look at attached image) so i checked and saw that it’s suppose to be a 68-70 big block master cylinder so now i have found dorman M73323 and was wondering if this is the right one i need or which one would i need that the pedal rod is the right length? do i have to run an adjustable rod? is it worth switching to dual or just put a oem one back in there? any advice would be appreciated!