I was at a stop light and across the way was
a ford tow truck. looked to be about a 1989?

it had a I beam front end with leaf springs

But it also had a set of coil springs under it.

the coil springs did not have shocks in the
center of them. they looked to be 6in diameter?

has any one seen this before ????

most likely it was an older "F450"... the original superduties...
they had solid I-beam fronts with leafs, & 10 lug wheels.
The coils were most likely just those cheezy "load enhancer" aftermarket bolt on stuff.