Modifing Seat Frame for detachable Headrest

[Paul-Ernest Levesque <pelevesque@globetrotter.net>]

I own a set of seat frame High Back (MKIV USA-1970-1973) and wish to
modified them to Low-Back (MKIV 1973-1975 & 1500) In other words I am
thinking of cutting the High Back headrest and install a Detachable Headrest
stalk fittings. Does anyone have done that? And where to buy that Headrest
Stalk fitting to be weld to the seat frame after cutting the high back
headrest support. All the frame of both seats type looks the same except the
top headrest. Any comments will be appreciated.
Paul-Ernest