Welcome to FBBO
you really should do another thread
but here's some sound suggestions **
if you are not worried about originality
stuff that won't 'butcher it up' like some will think
as a true daily driver at 80mph, I'd do a engine drivetrain swap
** or options I'll list below
*** more extensive options
or sell it & buys something else, that can do the job
**at a min. make it safe-r, do all the necessary safety stuff
so does it have a 318 ? (or a 225 slant 6 ?)
it should do 80mph easily with a lil' 318
**
if "geared properly"
**a nice efi, could (?) help cold & hot starts, it has a fuel bypass system
But;
**a bypass regulator w/electric fuel pump system
or factory 'evap' vapor seperator, with a return line/vapor line
going back to the tank, like 69-70 & later B-bodies BBs had
may require some mods to tank, for the return line
or
**install a later style fuel sending unit with them provisions
would help for a carb'd set-up too
keeps fuel cooler & constant flow
***
get rid of the castiron intake & **** carb,
help resolve the vapor-locking (or if need be reroute)
isolate or insulate the fuel lines from underhood heat
**a better carb & intake, a small 4bbl 600cfm Holley
on a Edelbrock Performer dual plane intake
&
**better free-er flowing exhaust
like 2-1/4" duals, with an h-pipe,
w/tailpipes all the way out the back, still be quiet
would also wake the lil' 318 up too
**add better brakes,
or
**at a min do new lines & flex hose
(Teflon lined stainless steel, so they don't swell)
&
**proper rear gearing for the speeds you want to drive
(***or maybe an overdrive trans)
&
***add some swaybars, frt & rear for handling
&
**good shocks, min.
**along with quality radial tires min. (***bigger wider (?)
it should be just fine
***otherwise do a modern engine & drivetrain swap
much more involved & more $$$
the lil' 318 should handle it, doing the proper stuff
won't be a rocket, but it's a
More Door anyway,
it's not meant/intended to be
IF you really like the car
I'm great at spending people's $$$
good luck & happy MoParing