Best Place to Buy Motor Mounts For my 383 Formula S.

Tim; Dont bother trying to find a new mount...they're next to impossible to find because most have cracked or broken LIKE YOURS.
Remove yours and have it welded and braced. Figure out how you wanna brace it.
After you get it all back together, I would recommend a Torque Strap to stop the mount from cracking again. Schumachers makes a nice one.
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Stephens Performance sent me one years ago that actually fit my 68 Dart GTS 383, but this was 20 years ago. I had bought 3 others before that did not fit.
Mine was a 4 speed Car also and the Stephens mount later broke.
Now a 727 Nostalgia Car. I had a steel mount specially welded up specifically for racing. Elephant ears will not fit an A Body Big Block K Frame.