Just what do I have here?

In 1975 my mother bought a
beautiful 73 LeMans Sport Coupe
GT from a local dealer here in
New Mexico who traded it from a
dealer in Calif. First off it did not
have a title and New Mexico had
to work hard to get it titled. (Kept
being told it was never meant for
purchase. Second the clutch went
out and finding one was hell to
say the least had to have one
made from a manufacturer in
calif.the engine is a 400 cid 2bbl
carb with a m22 Muncie 4 on the
floor. Guys this beauty does 60 in
first, 90 in second and virus the
needle in 3rd leaving 4th a
mystery. She came with (From
Calif) with duel glass packed
exhaust 60 series tires on the
rear,  full bench front seat, and no
badge on the front. Not even a
sign she had one she is 4 inches
wider (I bought a spare for parts,
that don't fit) and her hood has a
much larger v pattern and more
rounded for a LeMans. What I am
trying to find out is this is it a
CONCEPT car as the gauges and
grill say GTO but nothing else
refers to this and all her
modifications such as 60s on the
rear and no racking. Plus the fact
she was never meant to be titled
and the GM dealers were
constantly wanting it back. She
ours like a kitten with 116k miles
on her and I want to put her back
in show condition. Suggestions
please.