This from Dan McInerney:

Ford F550, housed at North Riverside and responds with a crew of two from there
MABAS Division 11 Haz Mat Unit 1100 Ford F550 Marion

MABAS Division 11 Haz Mat Unit 1100 was built by Marion on a Ford F-550, 4-door chassis. It is married to a 24′ trailer built by Alum-Line. Dan McInerney photo

MABAS Division 11 Haz Mat Unit 1100 Ford F550 Marion

This unit is housed in North Riverside and responds with a crew of 2 personnel. Dan McInerney photo

The unit is featured HERE on the Marion site and they offer a PDF drawing of the truck HERE and the trailer HERE.