Faced with a bad transmission, I'd rather rebuild the Slim-Jim, put the extra cash towards something else, & keep the car original.
If you just don't like the quirks that are inherent to the Slim-Jim's performance & want to replace it with something better, then that's another issue.
Tom Kasper in South Elgin, IL has been working on Slim-Jims since they were new. He advertises in Journey with Olds. He's done two Slim Jims for me in the past few years, & a third one in my '62 Starfire was rebuilt by him for the car's previous owner. Generally speaking, he upgrades each Slim-Jim to the last set of 1964 revisions. The most recent rebuild cost me around $1600, with me doing the removal & installation.
All of them work great. Granted, I wouldn't want to try beating the snot out of one, as it remains the weak link in the '61-4 drivetrain. Nonetheless, properly built & set up it's more than adequate for your average cruiser, as long as you're aware of its unusual qualities.
To me, that's part of the fun of driving these old cars- otherwise, why not just stick a crate motor into everything!
