Check for loose wheels. You never know. Beyond that possibly universal. Loose pinion nut on the center section? You said speed related. So also look for missing wheel weight.
68 Road Runner (383/4speed, post car w/decor pkg) - Major Project 69 Road Runner w/472 Hemi & 4 speed. 70 Challenger R/T SE EF8 w/ V9J, U - A32 - Major Project 2023 Ford Mach 1