Possibly engines only , always thought whole thing was Gradall but maybe they bought in the chassis like as you say the Brit crane makers, these things very popular in USA but never seemed to take off here ,perhaps they have more 'grade seperated interchanges ' They remain in production , little changed see link-
http://www.marketbook.co.uk/listingsdetail/detail.aspx?OHID=7584565&LP=MAT&