[Old Guy with 87 GT]

in my opinion ,i don't think it'll work...........i put a crane kit in mine and the retainers were alot different then the stock ones

the stock retainers were different on the exaust valves ,they put the spring hight lower then the intake valves .....were as the crane kit i got used the same retainers for int. and ex.
also the stock retainers were a diffrerent style then the crane retainers.......different way of holding onto spring ,the crane ones fit down into spring wereas the stock ones sorta sat ontop

i'm pretty novice ,so your machine shop guy might know more then me .....but i'd do some investagating on how he plans to do it .....make sure the retainers will seat stationary (that they won't shift around after a hundred miles )........and make sure you will have the specified spring hight with the stock retainers