i also use converted highbays... heres a pic of one.. lol you kinda can see the socket is still attatched to the bracket that is for the high bay
you cant see the ballast, as its mounted to the outside of the cab on the left hand side....
but to answer your orginal question, its a 50/50 chance the lamps will work.
the reason being is that some agro lamps are pulse start, while most high bay fixtures are not pulse start ballasts.
it alllll depends on the lamp man
ps- you can tell if your ballast is pulse start or not pretty easy. a pulse start MH halide ballast has an ignitor, a cap, and a transformer, just like a HPS... as a matter of fact, most pulse start ballasts can run MH or HPS by just switching the ignitor............
and another ps-
a probe start MH ballast (90% of all ballasts) has just a cap and a transformer