D'oh! My Wikipedia skills are weak.
While no jeeps during WW2 were equipped with a recoilless rifle, there were some jeeps mounted with bazookas.
This jeep belonged to the 60th IR of the 9th ID as part of the Intelligence and Reconnaissance (I&R) Platoon.
From what I've been able to find, this configuration wasn't intended for engaging tanks since the jeep would have to get within the effective range of the bazooka (150 yards or closer) but more of a shoot and scoot weapon intended to engage positions like machine gun nests and pill boxes.
Or maybe this jeep with a rocket launcher.
Or this one with a 37mm cannon.
ack-ack