M&D/GR intersection (minor M&D spoiler)

[Brian D. McCary]

Interesting observation.  Since the character and the object are both
real, it would have been easy to stick it into the earlier work.  However,
that would mean Pynchon was already interested in the background material
for M&D before finishing GR.  I know that someone posted info (or maybe
I read in a review) to the effect that he signed a contract in the early
eighties for two books, one about the MD line.  Does anyone know of any
sources indicating he was working on this book in the seventies?