"one thousand feet" or "one thousand foot"

Pronunciation of foot or of feet does not change significantly when embedded in a sentence. However, the choice of word depends on context, e.g.

It is a thousand-foot drop to the bottom of the cliff
It is a thousand feet to the bottom of the cliff.

In the first example, thousand-foot is used as an adjective, where it is regarded as a singular unit... as in the site The 1,000-Foot View.

In the second example, the noun, feet, must be plural.

Some more examples:

"He has a thousand-mile stare," as opposed to, "She has a thousand miles to go."
"It's a five-micron gap," as opposed to, "the gap is five microns."
"It's a thousand-dollar bicycle," vs. "The bicycle is a thousand dollars."
"Use a five-ohm resistor," but, "The resistor is five ohms."

sigh