Mysterious black vehicles

Guy comes out of prison and finds that his loot has disappeared. He is followed by black vehicles with shaded windows. I thought the title was something like "Sliders" or "Slithers" It turns out that the bad guys have bought these vehicles with his money intending to set up a legitimate business which went bust and they are afraid he will come after them - so they are going to get him first.

Please help me remember the title. It was probably in the '70s

Slither (1973)

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