I've come accross the interior body section from an early Minuteman
Missile.

Its the guidance housing section, sorta a truncated cone (very gentle
cone)
with a small glass window in the side (with heater unit).

(this bit without the avionics package
http://www.nasm.si.edu/research/dsh/...C-minutema.htm
)

The part designator matches the polaris (AN/DJ-20).

Its from before North American Aviation left Downey so it must be pre
'58.

Anyone suggest a value for such a thing (personally I like it as a nice
big chunk of nuclear missile for my home, but it won't fit through
doors)

Smonk