102 Priest's were converted into Kangaroo's in Normandy, these formerly served with the Commonwealth 'assault' divisions (the Infantry Divisions landed on D-Day), whose Artillery regiments were comprised only of Priests. However in late July '44 the Americans were facing a critical shortage of 105mm artillery shells, to ease the strain on the supply the three British and Canadian Infantry divisions operating Priests, replaced them with towed 25 Pounders, leaving a large number of Priests surplus to requirements.
Had it not been for the shortage of 105mm shells, it seems highly unlikely that the Kangaroo would've been created. As it was the Priest Kangaroo was vital in improving the mobility of the Commonwealth Infantry divisions, especially during the sealing of the Falaise pocket.
Aside from the Priest, and the aforementioned Ram tank conversions (IIRC produced in September '44 after the Priest's were returned to the Americans), Stuart's and Sherman III's (M4A2's) were converted into Kangaroo's too. The Sherman Kangaroo saw service only in Italy (where no Ram tanks were availible) alongside Priest Kangaroo's.